So you want to write Golden Kamuy fanfiction (and don't know much about Japanese history)
Golden Kamuy is an engrossing, densely-researched manga replete with historical details. You can learn a lot about Japanese history and especially Hokkaido and the Ainu people from reading it. But if you want to go further and write your own stories set in its timeline, you might face a few challenges.
This guide is intended to give you a good starting point for understanding some of the major historical touchstones of the manga, especially the Russo-Japanese War, the Shinsengumi, and life in the Meiji Era. By and large this is the product of my own research, doing an awful lot of googling, library dives, and pestering historian friends. It's not exhaustive, but I've tried to define terms and include my sources whenever possible, so that you can further your own research.
One thing to note: I am American, and (as you'll see below) a lot of the comparisons I make are based on that background. There are plenty of other historical points of reference that you may find more helpful, so please don't let this guide restrain you from seeking those out.

Western Analogues
It's not the greatest 1:1 comparison, but if you grew up on westerns, it's probably helpful to see Golden Kamuy in the context of the American Old West. Both are set on the frontier which has largely not been urbanized, the technology level is approximately the same, and both exist in the shadow of war -- the Mexican-American War and the Civil War for Americans; the Boshin War and the Russo-Japanese War for the Japanese. Also, both feature the eradication of native cultures by encroaching colonial forces. Golden Kamuy is sometimes even called a "hotpot western," after spaghetti westerns and other national reimaginings of the genre.
This can be a useful reference point when trying to figure out what Golden Kamuy characters might have available to them or have knowledge of, because there are way more resources in English on the Civil War and the Old West than on most Japanese conflicts. I'm told that the Second Boer War in South Africa is also a close analogue in terms of technology and logistics. Studying these can give you great insight into what soldiers would have carried, how illness and injury were treated, and how fast people could travel, among many other details.
Bakumatsu and the Boshin War
The Bakumatsu period (1853-1868) was the last days of the Tokugawa Shogunate, the military state which had governed Japan since the 1600s. While the Japanese Emperor remained in place and was revered as a holy figure, he had been functionally a figurehead for centuries. There was a caste system (though it's not the 1:1 analogue to European feudalism you were probably taught in school) which by the mid-19th century had eroded enough that it allowed some class mobility, such as peasants learning swordsmanship.
During the mid-1860s, political tensions in Japan were on the rise because of the increased presence of Western ships in Japanese harbors, after a long period of self-imposed cultural-economic isolationism. Political sentiments broadly fell into two camps:
Things eventually boiled over into the Boshin War, with several key domains (Satsuma among them) fighting in support of the Emperor's reinstatement. The Shogunate officially conceded to loyalist (pro-Emperor) forces in early 1868, kicking off the period known as the Meiji Era or Meiji Restoration.
Shinsengumi
The Shinsengumi (literally: "New Selected Corps") were a special police group instated by the Shogunate to quell loyalist dissent during the Bakumatsu period. They operated primarily in Kyoto, which was the economic and cultural capital at the time, and enjoyed pretty much full legal impunity to use whatever hardline tactics they liked, eg lots of killing and torture.
They were bad. Like, indefensible fascist murder cops bad. But whatever, Americans have a rap musical about a guy who owned slaves, so we're not really in any position to talk about other countries' thirsty revisionist history.
Hijikata Toshizou and Nagakura Shinpachi were two members of this Really Bad Murder Cop Gang. You've probably seen them and other Shinsengumi dudes show up in other media like Hakuouki, where they are usually all very handsome and heroic. I won't go through a complete biography on them here, but a few facts you might find of interest when writing:
Ezo Republic
Following the fall of the Shogunate in 1868, some of the survivors (among them the historical Hijikata Toshizou) who didn't take the loss well fled to Hokkaido to set up the Ezo Republic. It's important to note that though a lot of historians consider this the first (however shortly-lived) democracy in Japan, it was founded with the purpose of preserving the "traditional way of life" the samurai had enjoyed under the Shogunate. So basically it was the Bundy standoff. I'm sorry. Your historical faves are problematic.
All told, the Ezo Republic lasted exactly five months before surrendering to Imperial forces. Historical Hijikata did not live to see the republic's surrender: he died a few days previously during the last stages of the Battle of Hakodate. He entrusted his death poem, sword (the Izumi no Kami Kanesada), a photograph of himself, and strands of his hair to his page, who was either in his teens or early twenties, depending on your sources. Totally unrelated, it was common for samurai to take a younger lover-apprentice. I'm not saying but I'm definitely saying.
Life in the Meiji Era
The number one thing to remember when writing Meiji Era (1868 to 1912) settings like Golden Kamuy is that all of this is occurring just a few decades after a major civil war which tore the country apart. Many of those wounds are still fresh -- consider Inudou and Kadokura, whose families fought on opposing sides of the war, and how that family history informs how they treat Hijikata.
The Meiji Era was also a time of major commercial and industrial change as Japan opened itself to the West. We see Tsurumi using an early telephone and our heroes hijacking a dirigible, for instance. Even small details like the characters' clothing are informed by this: Sugimoto's scarf is not of Japanese make and Asirpa wears imported leggings under her traditional clothing.
Meiji also saw the official ending of Japan's caste system and a major shift in political power, which has repercussions for several of the characters. For instance, Ogata's given name "Hyakunosuke" is related to the samurai class, but there's a lot of evidence his mother's family was impoverished, so it's likely they were a samurai family disenfranchised for supporting the wrong side in the Boshin War. By contrast, the Koito family and Ogata's father are from Satsuma, which supported the Emperor, and they appear very well-off (see: Hanazawa's house, Koito's aristocratic mannerisms).
In other words, even though the Meiji Era officially did away with the old hierarchy, its echoes are still felt. The Boshin War is within living memory for many of the older characters like Tsurumi, Ienaga, and of course Hijikata and Nagakura.

Russo-Japanese War
The Russo-Japanese War, which most of Golden Kamuy's soldier characters participated in, ran from February 1904 to September 1905 in what is now the Liaoning province of eastern China, but what was referred to at the time as Manchuria. Broadly speaking, the war was the result of both Russia and Japan trying to expand their territories by seizing Port Arthur, a warm water port in the far south of the province, situated between Korea and the bulk of the Chinese mainland.
It's debated just how economically advantageous the port would've been for either country, and some critics suggest the war was more nationalistic posturing than pragmatic land grab. Though the Japanese "won" the war, it was a Pyrrhic victory, with no reparations from Russia and at least 58,000 dead.
The war was fought on land as well as by sea, but most of GK's military cast is infantry, so my recounting is going to focus on that. If you want a more detailed overview of the war from both Japanese and Russian perspectives (with only a little bit of patronizing white colonialism), I recommend Richard Connaughton's The War of the Rising Sun and the Tumbling Bear. It has maps. The maps are so useful.
Overview
The TL;DR of the Russo-Japanese War is that both Japanese and Russian armies did literally everything wrong, but the Russians did everything wrong a little bit worse. A recurring problem on the Russian side was that they kept trying to defend all fronts equally and as a result weren't able to respond adequately when the Japanese concentrated its forces. Lest you think the Japanese were doing something clever here, "concentrating its forces" is basically a euphemism for "throwing bodies at the problem until the Russians ran out of bullets and gave up."
Like I mentioned above, land conflict mainly took the form of trench warfare. A few general points:

Siege of Port Arthur
After first attempting to take the port by sea, the Japanese sent in huge swaths of soldiers to start taking over some key positions elsewhere in the lower peninsula, before attempting to attack Port Arthur again from the north. This is where the Battle of 203 Hill takes place, and it was by far the most protracted conflict in the war, lasting five months with an estimated 57,000 casualties (14,000 dead) for the Japanese and 31,000 (6,000 dead) for the Russians.
General Nogi Maresuke, who is probably one of the historical inspirations for Ogata's father, oversaw the Japanese Third Army which composed the bulk of 203 Hill's fighting strength. At the time, the 1st Division (based out of Tokyo; where Sugimoto served) and the 7th Division (based out of Hokkaido; where most of the other GK vets served) were both under the Third Army.
The 1st Division arrived when the battle first began in August 1904. The 7th Division was sent in to relieve them in late November, after most of the 1st Division's forces had been depleted. In other words, if you're writing Sugimoto encountering someone from the 7th Division (Ogata, Tanigaki, etc), it needs to be around late November 1904 or later.
Control of 203 Hill went back and forth several times before the Russians finally withdrew on January 2nd, 1905. After a period of rest and a memorial service for the dead, the Third Army was sent north to participate in the Battle of Mukden.
Events from the manga that occur during the Siege of Port Arthur/203 Hill (arranged roughly chronologically):
Battle of Mukden
The Third Army was tasked with shadowing the Second Army to conceal its movements from the Russians as it headed north. In late February 1905, the Third Army splintered off and headed northwest, catching the Russians in a pincer movement when it arrived at Mukden.
Mukden was the last significant land battle of the Russo-Japanese War and most of it was fought in a snowstorm, during an unusually cold winter. The temperature actually provided a tactical advantage to the Japanese, allowing them to follow the Russians across the Hun River when it was still frozen.
It was, for the most part, a battle of attrition, wearing the Russians down and overwhelming them from all sides until they were forced into retreat, and then giving pursuit. The battle officially ended on March 10, 1905, meaning the whole endeavor lasted about two weeks -- compared with the five months at Port Arthur. Despite this, casualties were steep on both sides: 75,000 for the Japanese (15,000 dead), 88,000 for the Russians (8,000 dead).
Events from the manga which occurred at Mukden (rough chronological order):
There are a few good resources on Imperial Japanese Army uniforms and the equipment they carried, if your story calls for those details. I found this book in the Men-at-Arms series a good reference, and it's available as an ebook, which is a plus.
For other color references, I actually mostly relied on Google Image Search. You will want to search specifically for uniforms during the Russo-Japanese War, however, because if you just search for the Imperial Japanese Army you're likely to get results for World War II uniforms, which were different.
Death
Because casualties were so steep, the Japanese often could not cremate the bodies or their deceased. Instead, medics cut out the corpse's hyoid bone (some documents translate this as the Adam's apple) and shipped this back to the soldier's family.
Why the hyoid bone? In Japanese Buddhist funeral customs, it's supposed to indicate the state of your soul. If the bone clearly resembles a sitting Buddha, it means your karma was good. If it's not visible, you led a sinful life and were going to reincarnate as something worse. So, if the army was going to send one part of a soldier's remains back to his family, it was going to be something that could (hopefully) give them peace of mind.
It should be noted not all soldiers' remains made it back to their families. Sugimoto is only able to present Toraji's family with his finger bones, and they express gratitude to even receive that much.

Post-War
The Russo-Japanese War officially ended on September 5th, 1905, but the Third Army was not formally demobilized until January 1906. It's therefore pretty likely that the 1st and 7th Divisions spent several more months in Manchuria following the signing of the peace treaty.
What would they have been doing? Likely clean-up and assisting with reconstruction efforts. The Japanese brass had been adamant about keeping civilians as far out of the war as possible, but a lot of places had still sustained damage, especially Port Arthur which had seen a lot of shelling. It probably wasn't a pleasant experience, seeing as the war had financially drained the country and it was in no real position to rebuild anything. The lack of reparations from Russia didn't help.
Soldiers in the Third Army might also have been overseeing the release of POWs, assisting with the demobilization of other units, or serving as a transitional peacekeeping force. There's not actually a lot of data on this available in English, but these are all Normal War Things that a victorious army would've been expected to participate in.
Some companies may have started to get shipped back ahead of complete demobilization, so it's a little difficult to say when, exactly, Sugimoto or any of the other characters would've gotten back to Japan. Even once they arrived, there would be a period of outprocessing (exit medical exam, settling of pay, etc) and the actual transporting of soldiers back to their home provinces. We're also not sure exactly what the circumstances were when Sugimoto was discharged, whether this occurred before his division's demobilization, if he had a court-martial... you get the idea.
We do know it's spring (most likely March~May 1906) when Sugimoto brings Toraji's family his remains, but we don't know how soon this is after his return and/or discharge. Kamuy Central has a lot of data that places Sugimoto meeting Asirpa probably around February 1907.
Soldiers who elected to stay on after their terms of service would likely get moved around to new assignments based on domestic need. Hokkaido's 7th Division was a semi-permanent colonization/peacekeeping force which already brought in many of its soldiers from elsewhere, so it's not unreasonable that some of the 7th Division soldiers we see hanging around Tsurumi now but don't see in flashbacks (like Usami) served in other divisions during the war. They could also have joined after the war was over, like Koito.
Accuracy
"Do I really need to include all this? Doesn't sensei fudge some details too?"
Yes, absolutely he does. For one thing, all the soldiers we see in flashbacks are a lot cleaner and less emaciated than they probably would've been in reality. However grotesque and bloody the war scenes are in the manga, the reality was a lot worse. Some of the passages in The War of the Rising Sun and the Tumbling Bear are straight up haunting.
And really, at the end of the day, this is fanfic. It's meant to be for fun, so if worrying about the historical accuracy gets in the way of that fun for you, just leave it aside and write what you like! But a lot of fanwriters (like me) do enjoy research and getting the fiddly little details right. And if that's you, I hope this guide provides a good starting place.
"You messed up XYZ!"
I definitely appreciate any assistance in making this guide more accurate and useful. Please leave me a comment or hit me up on Twitter @robotdere!
Many thanks to the following individuals for their feedback and support: Emma, Icie, AJ, my historian friends Maggie and Troy, Alex, and of course Kamuy Central and the wonderful history geeks scanlating the manga at Everyday Heroes. (Please support the official releases.)
This guide is intended to give you a good starting point for understanding some of the major historical touchstones of the manga, especially the Russo-Japanese War, the Shinsengumi, and life in the Meiji Era. By and large this is the product of my own research, doing an awful lot of googling, library dives, and pestering historian friends. It's not exhaustive, but I've tried to define terms and include my sources whenever possible, so that you can further your own research.
One thing to note: I am American, and (as you'll see below) a lot of the comparisons I make are based on that background. There are plenty of other historical points of reference that you may find more helpful, so please don't let this guide restrain you from seeking those out.

Western Analogues
It's not the greatest 1:1 comparison, but if you grew up on westerns, it's probably helpful to see Golden Kamuy in the context of the American Old West. Both are set on the frontier which has largely not been urbanized, the technology level is approximately the same, and both exist in the shadow of war -- the Mexican-American War and the Civil War for Americans; the Boshin War and the Russo-Japanese War for the Japanese. Also, both feature the eradication of native cultures by encroaching colonial forces. Golden Kamuy is sometimes even called a "hotpot western," after spaghetti westerns and other national reimaginings of the genre.
This can be a useful reference point when trying to figure out what Golden Kamuy characters might have available to them or have knowledge of, because there are way more resources in English on the Civil War and the Old West than on most Japanese conflicts. I'm told that the Second Boer War in South Africa is also a close analogue in terms of technology and logistics. Studying these can give you great insight into what soldiers would have carried, how illness and injury were treated, and how fast people could travel, among many other details.
Bakumatsu and the Boshin War
The Bakumatsu period (1853-1868) was the last days of the Tokugawa Shogunate, the military state which had governed Japan since the 1600s. While the Japanese Emperor remained in place and was revered as a holy figure, he had been functionally a figurehead for centuries. There was a caste system (though it's not the 1:1 analogue to European feudalism you were probably taught in school) which by the mid-19th century had eroded enough that it allowed some class mobility, such as peasants learning swordsmanship.
During the mid-1860s, political tensions in Japan were on the rise because of the increased presence of Western ships in Japanese harbors, after a long period of self-imposed cultural-economic isolationism. Political sentiments broadly fell into two camps:
- The Shogunate has failed to protect Japan from foreigners, and the Emperor needs to be restored as the actual head of state.
- The Shogunate can oust the foreigners just fine, and the Emperor is better off remaining a figurehead.
Things eventually boiled over into the Boshin War, with several key domains (Satsuma among them) fighting in support of the Emperor's reinstatement. The Shogunate officially conceded to loyalist (pro-Emperor) forces in early 1868, kicking off the period known as the Meiji Era or Meiji Restoration.
Shinsengumi
The Shinsengumi (literally: "New Selected Corps") were a special police group instated by the Shogunate to quell loyalist dissent during the Bakumatsu period. They operated primarily in Kyoto, which was the economic and cultural capital at the time, and enjoyed pretty much full legal impunity to use whatever hardline tactics they liked, eg lots of killing and torture.
They were bad. Like, indefensible fascist murder cops bad. But whatever, Americans have a rap musical about a guy who owned slaves, so we're not really in any position to talk about other countries' thirsty revisionist history.
Hijikata Toshizou and Nagakura Shinpachi were two members of this Really Bad Murder Cop Gang. You've probably seen them and other Shinsengumi dudes show up in other media like Hakuouki, where they are usually all very handsome and heroic. I won't go through a complete biography on them here, but a few facts you might find of interest when writing:
- Hijikata and the leader of the Shinsengumi, Kondo Isami, both hailed from the peasant class rather than samurai, extremely unusual for the time.
- That being said, they weren't impoverished. Both came from wealthy farming families and had access to education and swordsmanship training that many peasants could only dream of.
- Hijikata was big on poetry and I'm honestly surprised Noda hasn't depicted him composing a single haiku in the manga yet.
- Unlike most of his comrades, Nagakura did indeed survive the war. He retired to Hokkaido and a lot of what we know about the Shinsengumi today comes from his memoirs.
Ezo Republic
Following the fall of the Shogunate in 1868, some of the survivors (among them the historical Hijikata Toshizou) who didn't take the loss well fled to Hokkaido to set up the Ezo Republic. It's important to note that though a lot of historians consider this the first (however shortly-lived) democracy in Japan, it was founded with the purpose of preserving the "traditional way of life" the samurai had enjoyed under the Shogunate. So basically it was the Bundy standoff. I'm sorry. Your historical faves are problematic.
All told, the Ezo Republic lasted exactly five months before surrendering to Imperial forces. Historical Hijikata did not live to see the republic's surrender: he died a few days previously during the last stages of the Battle of Hakodate. He entrusted his death poem, sword (the Izumi no Kami Kanesada), a photograph of himself, and strands of his hair to his page, who was either in his teens or early twenties, depending on your sources. Totally unrelated, it was common for samurai to take a younger lover-apprentice. I'm not saying but I'm definitely saying.
Life in the Meiji Era
The number one thing to remember when writing Meiji Era (1868 to 1912) settings like Golden Kamuy is that all of this is occurring just a few decades after a major civil war which tore the country apart. Many of those wounds are still fresh -- consider Inudou and Kadokura, whose families fought on opposing sides of the war, and how that family history informs how they treat Hijikata.
The Meiji Era was also a time of major commercial and industrial change as Japan opened itself to the West. We see Tsurumi using an early telephone and our heroes hijacking a dirigible, for instance. Even small details like the characters' clothing are informed by this: Sugimoto's scarf is not of Japanese make and Asirpa wears imported leggings under her traditional clothing.
Meiji also saw the official ending of Japan's caste system and a major shift in political power, which has repercussions for several of the characters. For instance, Ogata's given name "Hyakunosuke" is related to the samurai class, but there's a lot of evidence his mother's family was impoverished, so it's likely they were a samurai family disenfranchised for supporting the wrong side in the Boshin War. By contrast, the Koito family and Ogata's father are from Satsuma, which supported the Emperor, and they appear very well-off (see: Hanazawa's house, Koito's aristocratic mannerisms).
In other words, even though the Meiji Era officially did away with the old hierarchy, its echoes are still felt. The Boshin War is within living memory for many of the older characters like Tsurumi, Ienaga, and of course Hijikata and Nagakura.

Russo-Japanese War
The Russo-Japanese War, which most of Golden Kamuy's soldier characters participated in, ran from February 1904 to September 1905 in what is now the Liaoning province of eastern China, but what was referred to at the time as Manchuria. Broadly speaking, the war was the result of both Russia and Japan trying to expand their territories by seizing Port Arthur, a warm water port in the far south of the province, situated between Korea and the bulk of the Chinese mainland.
It's debated just how economically advantageous the port would've been for either country, and some critics suggest the war was more nationalistic posturing than pragmatic land grab. Though the Japanese "won" the war, it was a Pyrrhic victory, with no reparations from Russia and at least 58,000 dead.
The war was fought on land as well as by sea, but most of GK's military cast is infantry, so my recounting is going to focus on that. If you want a more detailed overview of the war from both Japanese and Russian perspectives (with only a little bit of patronizing white colonialism), I recommend Richard Connaughton's The War of the Rising Sun and the Tumbling Bear. It has maps. The maps are so useful.
Overview
The TL;DR of the Russo-Japanese War is that both Japanese and Russian armies did literally everything wrong, but the Russians did everything wrong a little bit worse. A recurring problem on the Russian side was that they kept trying to defend all fronts equally and as a result weren't able to respond adequately when the Japanese concentrated its forces. Lest you think the Japanese were doing something clever here, "concentrating its forces" is basically a euphemism for "throwing bodies at the problem until the Russians ran out of bullets and gave up."
Like I mentioned above, land conflict mainly took the form of trench warfare. A few general points:
- Combat engineers (such as Kiroranke) saw to much of the trench digging, laying barbed wire, etc.
- Sandbags were in constant short supply. Dead bodies of comrades were often used instead.
- No tanks! This is before tanks were A Thing.
- They did have cannons though.
- Horses were rare, reserved for cavalry units, supply wagons, and some officers.
- Illness was extremely common in the trenches and in camps. By this I mean diarrhea. So much diarrhea.
- It's called the first "modern war" but it still had the hallmarks of a lot of 19th century warfare, especially the whole aristocracy sitting around sipping tea and attending dinners while enlisted men starved to death in freezing trenches. You know. That bit.

Siege of Port Arthur
After first attempting to take the port by sea, the Japanese sent in huge swaths of soldiers to start taking over some key positions elsewhere in the lower peninsula, before attempting to attack Port Arthur again from the north. This is where the Battle of 203 Hill takes place, and it was by far the most protracted conflict in the war, lasting five months with an estimated 57,000 casualties (14,000 dead) for the Japanese and 31,000 (6,000 dead) for the Russians.
General Nogi Maresuke, who is probably one of the historical inspirations for Ogata's father, oversaw the Japanese Third Army which composed the bulk of 203 Hill's fighting strength. At the time, the 1st Division (based out of Tokyo; where Sugimoto served) and the 7th Division (based out of Hokkaido; where most of the other GK vets served) were both under the Third Army.
The 1st Division arrived when the battle first began in August 1904. The 7th Division was sent in to relieve them in late November, after most of the 1st Division's forces had been depleted. In other words, if you're writing Sugimoto encountering someone from the 7th Division (Ogata, Tanigaki, etc), it needs to be around late November 1904 or later.
Control of 203 Hill went back and forth several times before the Russians finally withdrew on January 2nd, 1905. After a period of rest and a memorial service for the dead, the Third Army was sent north to participate in the Battle of Mukden.
Events from the manga that occur during the Siege of Port Arthur/203 Hill (arranged roughly chronologically):
- Ogata murders Yuusaku
- Kiroranke masters his improvised grenades
- The prologue takes place
- Tanigaki meets Sugimoto and shares his kane mochi with him
- Tanigaki tracks down his brother-in-law Kenkichi
Battle of Mukden
The Third Army was tasked with shadowing the Second Army to conceal its movements from the Russians as it headed north. In late February 1905, the Third Army splintered off and headed northwest, catching the Russians in a pincer movement when it arrived at Mukden.
Mukden was the last significant land battle of the Russo-Japanese War and most of it was fought in a snowstorm, during an unusually cold winter. The temperature actually provided a tactical advantage to the Japanese, allowing them to follow the Russians across the Hun River when it was still frozen.
It was, for the most part, a battle of attrition, wearing the Russians down and overwhelming them from all sides until they were forced into retreat, and then giving pursuit. The battle officially ended on March 10, 1905, meaning the whole endeavor lasted about two weeks -- compared with the five months at Port Arthur. Despite this, casualties were steep on both sides: 75,000 for the Japanese (15,000 dead), 88,000 for the Russians (8,000 dead).
Events from the manga which occurred at Mukden (rough chronological order):
- Toraji tells Sugimoto his plans for after the war
- Tsurumi and Tsukishima are injured
- Toraji dies
There are a few good resources on Imperial Japanese Army uniforms and the equipment they carried, if your story calls for those details. I found this book in the Men-at-Arms series a good reference, and it's available as an ebook, which is a plus.
For other color references, I actually mostly relied on Google Image Search. You will want to search specifically for uniforms during the Russo-Japanese War, however, because if you just search for the Imperial Japanese Army you're likely to get results for World War II uniforms, which were different.
Death
Because casualties were so steep, the Japanese often could not cremate the bodies or their deceased. Instead, medics cut out the corpse's hyoid bone (some documents translate this as the Adam's apple) and shipped this back to the soldier's family.
Why the hyoid bone? In Japanese Buddhist funeral customs, it's supposed to indicate the state of your soul. If the bone clearly resembles a sitting Buddha, it means your karma was good. If it's not visible, you led a sinful life and were going to reincarnate as something worse. So, if the army was going to send one part of a soldier's remains back to his family, it was going to be something that could (hopefully) give them peace of mind.
It should be noted not all soldiers' remains made it back to their families. Sugimoto is only able to present Toraji's family with his finger bones, and they express gratitude to even receive that much.

Post-War
The Russo-Japanese War officially ended on September 5th, 1905, but the Third Army was not formally demobilized until January 1906. It's therefore pretty likely that the 1st and 7th Divisions spent several more months in Manchuria following the signing of the peace treaty.
What would they have been doing? Likely clean-up and assisting with reconstruction efforts. The Japanese brass had been adamant about keeping civilians as far out of the war as possible, but a lot of places had still sustained damage, especially Port Arthur which had seen a lot of shelling. It probably wasn't a pleasant experience, seeing as the war had financially drained the country and it was in no real position to rebuild anything. The lack of reparations from Russia didn't help.
Soldiers in the Third Army might also have been overseeing the release of POWs, assisting with the demobilization of other units, or serving as a transitional peacekeeping force. There's not actually a lot of data on this available in English, but these are all Normal War Things that a victorious army would've been expected to participate in.
Some companies may have started to get shipped back ahead of complete demobilization, so it's a little difficult to say when, exactly, Sugimoto or any of the other characters would've gotten back to Japan. Even once they arrived, there would be a period of outprocessing (exit medical exam, settling of pay, etc) and the actual transporting of soldiers back to their home provinces. We're also not sure exactly what the circumstances were when Sugimoto was discharged, whether this occurred before his division's demobilization, if he had a court-martial... you get the idea.
We do know it's spring (most likely March~May 1906) when Sugimoto brings Toraji's family his remains, but we don't know how soon this is after his return and/or discharge. Kamuy Central has a lot of data that places Sugimoto meeting Asirpa probably around February 1907.
Soldiers who elected to stay on after their terms of service would likely get moved around to new assignments based on domestic need. Hokkaido's 7th Division was a semi-permanent colonization/peacekeeping force which already brought in many of its soldiers from elsewhere, so it's not unreasonable that some of the 7th Division soldiers we see hanging around Tsurumi now but don't see in flashbacks (like Usami) served in other divisions during the war. They could also have joined after the war was over, like Koito.
Accuracy
"Do I really need to include all this? Doesn't sensei fudge some details too?"
Yes, absolutely he does. For one thing, all the soldiers we see in flashbacks are a lot cleaner and less emaciated than they probably would've been in reality. However grotesque and bloody the war scenes are in the manga, the reality was a lot worse. Some of the passages in The War of the Rising Sun and the Tumbling Bear are straight up haunting.
And really, at the end of the day, this is fanfic. It's meant to be for fun, so if worrying about the historical accuracy gets in the way of that fun for you, just leave it aside and write what you like! But a lot of fanwriters (like me) do enjoy research and getting the fiddly little details right. And if that's you, I hope this guide provides a good starting place.
"You messed up XYZ!"
I definitely appreciate any assistance in making this guide more accurate and useful. Please leave me a comment or hit me up on Twitter @robotdere!
Many thanks to the following individuals for their feedback and support: Emma, Icie, AJ, my historian friends Maggie and Troy, Alex, and of course Kamuy Central and the wonderful history geeks scanlating the manga at Everyday Heroes. (Please support the official releases.)