CANON HISTORY: First, to clarify, I will be playing Saitou mainly following the events of the movie, Kyoto Ranbu. Because the movie doesn't really go into pre-Shinsengumi events, however, I'll be drawing on events from Reimeiroku, the anime/video game prequel to Hakuouki, so that I can fill in his backstory. Given that major events don't really change between various versions of Hakuouki, I figure it should be fine to assume that the major events of Reimeiroku are still true. That said, I'll obviously be using examples from all over for the personality section, but as far as what's "canon" for him goes, it will be the events of the movie. The reason for this is mostly just because it'll be easier for me to keep track of this way, since the plot is linear, mostly focuses on the major events, and the outcome doesn't rely on specific choices made by the protagonist. Anyway!
Not much is known about the clan that Saitou used to serve, but the fact that he had one at all was something that set him apart from most of the men at Shiei Hall. Saitou dreamed of being a warrior, and having a clan to serve gave him an advantage over many of the men who gathered there, men who had a similar dream but lacked a lord for various reasons. Unfortunately, Saitou had a "problem" that would completely negate this advantage, and it was a problem that he had very little control over—he was born left-handed. No matter where he went, Saitou was shunned as a swordsman due to this one simple fact. Even though he was strong and defeated every single opponent he came across fair and square, he was called a cheater and kicked out of every dojo he stepped foot in, simply because a left-handed stance was considered "wrong" and he refused to change it. Generally, left-handed students would have their stance corrected while learning swordsmanship, so left-handed swordsman literally did not exist, but Saitou never went for that. Why should he fix something that's not broken? There was never anything wrong with him in the first place. So Saitou simply moved on, continuing to search for an opponent that could back up his words with skill.
It was while Saitou went from dojo to dojo challenging others that he eventually came upon Shiei Hall. Here, he challenged Souji Okita, the dojo's star pupil, and was actually defeated—technically. Souji was the first person Saitou had ever faced who actually presented him with a challenge, and even though Souji managed to land the first hit, the two refused to stop fighting until Toshizou Hijikata intervened and ordered the others to forcibly separate them. Even though he lost, Saitou expected to be kicked out once again, but what actually happened came as a complete shock to him: Isami Kondou, the master of the dojo, had nothing but praise for him, and Hijikata explained that a victory is a victory and anyone who blamed Saitou's left-handedness for their loss simply couldn't accept defeat. This was the first time that Saitou wasn't criticized for his technique, but his actual skill, and it was the first time that anyone had openly approved of what he was capable of. Saitou was truly in awe.
Saitou began to spend more time at Shiei Hall after this. Even though he was shy, the others welcomed him with open arms. However, Saitou did not wish to be a burden to the only people who had ever accepted him, so he didn't stay at Shiei Hall like the others did. Unlike people like Souji or Heisuke or Shinpachi, who had nowhere else to go, Saitou had somewhere to return to, so he only came by to train, spar, and have meals (which he paid for) before going on his way. Eventually, though, Saitou stopped coming to Shiei Hall, and no one knew why. Sometime after he had started to frequent the dojo, he had been challenged to a duel by the son of a hatamoto family, who asked that they use real swords as opposed to bamboo or wooden ones. As a samurai, Saitou thought the son would be able to accept the consequences of the match, so he agreed to the duel and won. Once again, things didn't turn out the way Saitou had expected, but this time, the outcome was not in his favor: despite winning the match fairly, he was viewed as a murderer for having killed his opponent, and was forced to leave his clan. Not having a clan meant not having a lord, and not having a lord was kind of a problem—having a lord to serve was a key part of being a samurai, so now that he didn't have one, Saitou saw no point in carrying his swords.
So he stopped. The thing is, after he stopped carrying his swords, Saitou realized that he was essentially invisible to the world. There was nothing that set him apart from the number of other people that he shared the world with. If he wasn't a samurai, then he might as well not even exist at all. That was when Saitou heard about the Roshigumi, a group of men who dreamed of being warriors and protecting the people and their city from lawless ronin. Not only that, but this Roshigumi also happened to be made up of the people he had met at Shiei Hall. That pretty much settled it—no longer having a lord but still wishing to be a samurai, Saitou sought out the Roshigumi's headquarters in Kyoto and formally requested to join. Just like the first time, he was welcomed with open arms, and Saitou swore that he would do whatever he could for the sake of the Roshigumi in order to repay them for giving him the chance to live again.
As a result, Saitou had found his purpose. He fought alongside the Roshigumi as it struggled to make a name for itself, although it usually didn't enjoy an especially positive reputation. Even though the shogunate approved of their existence and allowed them to operate, the Roshigumi wasn't an official part of the shogunate's forces, so their support was pretty limited. During this time of struggle, the Roshigumi was approached by Doctor Kodou Yukimura, who claimed to have the answer to one of their problems, which was a constant lack of manpower. This solution was called the Water of Life, a "medicine" capable of giving ordinary humans supernatural strength and healing abilities. The medicine had a few (read: a lot) of kinks that needed to be worked out, but if they could manage to refine it, it could turn out to be a powerful tool. Kondou and Hijikata hated the idea of treating their own men like test subjects, but they were eventually persuaded with the idea that it could be used on men who were going to be told to kill themselves anyway. Whenever they broke the rules, they would be given a choice: they could kill themselves, or they could take the Water of Life. The compromise was effective, and the Roshigumi now had a chance—they would lose fewer men this way and they had a shot at a weapon that could give them an edge in the fight. Whether they liked it or not, it was probably their only chance if they hoped to succeed, so they went for it.
Regardless of his personal feelings on the matter, Saitou supported the Roshigumi through everything—he supported them through Commander Kamou Serizawa's terrorizing reign, helped keep the secret of the Water of Life and the furies, and fought alongside the Roshigumi against ronin and rebels alike until the Aizu domain officially acknowledged them, giving them a new name. The Roshigumi became the Shinsengumi, finally giving them a piece of the recognition they deserved.
Unfortunately, the Shinsengumi still had the whole "fury" issue to deal with, and for that, they sought out Kodou Yukimura once more, hoping for his help in refining the Water of Life. Kodou was nowhere to be found, but they did run into Chizuru, his daughter, and decided to keep her around for the sake of finding her father. While the Shinsengumi continued to serve the shogun, they simultaneously continued their search for Kodou, but to no avail. As they worked, the Shinsengumi encountered yet another internal dilemma, one not very different from their previous one with former commander Serizawa—after discovering the Shinsengumi's involvement with the fury research, a newer member, Kashitarou Itou, decided to break away from the Shinsengumi and take some of its men with him to form a new group. Believing in Itou's politics, many men chose to go with him to fight on his side. Among the men who left the Shinsengumi was someone that no one had ever expected—Hajime Saitou.
But little did anyone know, Saitou hadn't left for his own reasons—he had left for the sake of the Shinsengumi. He left because he'd been asked to so that he could keep an eye on Itou and his men. As far as anyone else knew, though, Saitou was no longer a member of the Shinsengumi, but rather, a member of the newly-formed Guardians of the Imperial Tomb.
Hajime Saitou / Hakuouki / Reserved
Not much is known about the clan that Saitou used to serve, but the fact that he had one at all was something that set him apart from most of the men at Shiei Hall. Saitou dreamed of being a warrior, and having a clan to serve gave him an advantage over many of the men who gathered there, men who had a similar dream but lacked a lord for various reasons. Unfortunately, Saitou had a "problem" that would completely negate this advantage, and it was a problem that he had very little control over—he was born left-handed. No matter where he went, Saitou was shunned as a swordsman due to this one simple fact. Even though he was strong and defeated every single opponent he came across fair and square, he was called a cheater and kicked out of every dojo he stepped foot in, simply because a left-handed stance was considered "wrong" and he refused to change it. Generally, left-handed students would have their stance corrected while learning swordsmanship, so left-handed swordsman literally did not exist, but Saitou never went for that. Why should he fix something that's not broken? There was never anything wrong with him in the first place. So Saitou simply moved on, continuing to search for an opponent that could back up his words with skill.
It was while Saitou went from dojo to dojo challenging others that he eventually came upon Shiei Hall. Here, he challenged Souji Okita, the dojo's star pupil, and was actually defeated—technically. Souji was the first person Saitou had ever faced who actually presented him with a challenge, and even though Souji managed to land the first hit, the two refused to stop fighting until Toshizou Hijikata intervened and ordered the others to forcibly separate them. Even though he lost, Saitou expected to be kicked out once again, but what actually happened came as a complete shock to him: Isami Kondou, the master of the dojo, had nothing but praise for him, and Hijikata explained that a victory is a victory and anyone who blamed Saitou's left-handedness for their loss simply couldn't accept defeat. This was the first time that Saitou wasn't criticized for his technique, but his actual skill, and it was the first time that anyone had openly approved of what he was capable of. Saitou was truly in awe.
Saitou began to spend more time at Shiei Hall after this. Even though he was shy, the others welcomed him with open arms. However, Saitou did not wish to be a burden to the only people who had ever accepted him, so he didn't stay at Shiei Hall like the others did. Unlike people like Souji or Heisuke or Shinpachi, who had nowhere else to go, Saitou had somewhere to return to, so he only came by to train, spar, and have meals (which he paid for) before going on his way. Eventually, though, Saitou stopped coming to Shiei Hall, and no one knew why. Sometime after he had started to frequent the dojo, he had been challenged to a duel by the son of a hatamoto family, who asked that they use real swords as opposed to bamboo or wooden ones. As a samurai, Saitou thought the son would be able to accept the consequences of the match, so he agreed to the duel and won. Once again, things didn't turn out the way Saitou had expected, but this time, the outcome was not in his favor: despite winning the match fairly, he was viewed as a murderer for having killed his opponent, and was forced to leave his clan. Not having a clan meant not having a lord, and not having a lord was kind of a problem—having a lord to serve was a key part of being a samurai, so now that he didn't have one, Saitou saw no point in carrying his swords.
So he stopped. The thing is, after he stopped carrying his swords, Saitou realized that he was essentially invisible to the world. There was nothing that set him apart from the number of other people that he shared the world with. If he wasn't a samurai, then he might as well not even exist at all. That was when Saitou heard about the Roshigumi, a group of men who dreamed of being warriors and protecting the people and their city from lawless ronin. Not only that, but this Roshigumi also happened to be made up of the people he had met at Shiei Hall. That pretty much settled it—no longer having a lord but still wishing to be a samurai, Saitou sought out the Roshigumi's headquarters in Kyoto and formally requested to join. Just like the first time, he was welcomed with open arms, and Saitou swore that he would do whatever he could for the sake of the Roshigumi in order to repay them for giving him the chance to live again.
As a result, Saitou had found his purpose. He fought alongside the Roshigumi as it struggled to make a name for itself, although it usually didn't enjoy an especially positive reputation. Even though the shogunate approved of their existence and allowed them to operate, the Roshigumi wasn't an official part of the shogunate's forces, so their support was pretty limited. During this time of struggle, the Roshigumi was approached by Doctor Kodou Yukimura, who claimed to have the answer to one of their problems, which was a constant lack of manpower. This solution was called the Water of Life, a "medicine" capable of giving ordinary humans supernatural strength and healing abilities. The medicine had a few (read: a lot) of kinks that needed to be worked out, but if they could manage to refine it, it could turn out to be a powerful tool. Kondou and Hijikata hated the idea of treating their own men like test subjects, but they were eventually persuaded with the idea that it could be used on men who were going to be told to kill themselves anyway. Whenever they broke the rules, they would be given a choice: they could kill themselves, or they could take the Water of Life. The compromise was effective, and the Roshigumi now had a chance—they would lose fewer men this way and they had a shot at a weapon that could give them an edge in the fight. Whether they liked it or not, it was probably their only chance if they hoped to succeed, so they went for it.
Regardless of his personal feelings on the matter, Saitou supported the Roshigumi through everything—he supported them through Commander Kamou Serizawa's terrorizing reign, helped keep the secret of the Water of Life and the furies, and fought alongside the Roshigumi against ronin and rebels alike until the Aizu domain officially acknowledged them, giving them a new name. The Roshigumi became the Shinsengumi, finally giving them a piece of the recognition they deserved.
Unfortunately, the Shinsengumi still had the whole "fury" issue to deal with, and for that, they sought out Kodou Yukimura once more, hoping for his help in refining the Water of Life. Kodou was nowhere to be found, but they did run into Chizuru, his daughter, and decided to keep her around for the sake of finding her father. While the Shinsengumi continued to serve the shogun, they simultaneously continued their search for Kodou, but to no avail. As they worked, the Shinsengumi encountered yet another internal dilemma, one not very different from their previous one with former commander Serizawa—after discovering the Shinsengumi's involvement with the fury research, a newer member, Kashitarou Itou, decided to break away from the Shinsengumi and take some of its men with him to form a new group. Believing in Itou's politics, many men chose to go with him to fight on his side. Among the men who left the Shinsengumi was someone that no one had ever expected—Hajime Saitou.
But little did anyone know, Saitou hadn't left for his own reasons—he had left for the sake of the Shinsengumi. He left because he'd been asked to so that he could keep an eye on Itou and his men. As far as anyone else knew, though, Saitou was no longer a member of the Shinsengumi, but rather, a member of the newly-formed Guardians of the Imperial Tomb.