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 Sougo is a sadist. He enjoys torturing people, teasing them, anything that will scare them or make them afraid of him. He doesn't care if he knows you or not, he will still tease you, or if you put up a fight, he will fight you. He doesn't like to lose, so he's not going to just let someone take him down. Canonly he's a cop — or to be more specific, he's a member of the Shinsengumi — so he has skills needed to defend himself and put up a good fight. He's a master at kenjutsu, and is said to be the best swordsman of the Shinsengumi. He's super quick and he can sense a person's movements, and is therefore able to dodge strikes against him (of course if it's a group of people, that's an unrealistic expectation, though he will still try). Despite being good at the sword, he often uses a bazooka just because he can. And because it makes things go boom. Even though he slacks off on his job often, napping, watching TV, being lazy or whatever when he should be doing something else, he still has respect for his duty as a cop. He might threaten to kill people to scare them, but he won't actually do it if it's not within his line of duty. Hijikata, the Vice Chief of the Shinsengumi, is the one person who gets it the worst, as Sougo attacks and annoys him to no end. Every day, Sougo threatens to kill or injure Hijikata in some way shape or form. Sougo so badly wants the Vice Chief position, so he really wants Hijikata out of the way.

He's usually very stoic and deadpan, never showing any emotion and always keeping his guard up; way up. Because of how he acts, he's considered a heartless, cold person. He likes to come across as someone who doesn't care about anyone else other than himself. He's actually just very private about his real thoughts and feelings — feelings, something he does actually have. He doesn't talk about his own life much at all, and is usually off on his own, even when he's with members of the Shinsengumi.

Sougo's parents died when he was little, so his older sister, Mitsuba, took care of him. Mitsuba is Sougo's entire universe. She did everything for him, so much so that she hardly even made time to take care of herself. Since the death of his parents, Sougo became a distant child, a loner even, and didn't have friends, hence why he's so attached to his sister. Sougo eventually met Isao Kondo (Commander of the Shinsengumi aka the boss), who saw something in Sougo, and that's when Sougo started training and developed his fighting skills. Kondo became the one friend Sougo had, and Sougo was on cloud nine having Kondo and Mitsuba around.

Then Kondo found Hijikata and also had him come train at his dojo. It started becoming about Hijikata, and Sougo didn't like it. At all. Sougo was usually always ready to train come morning, but since Hijikata joined them, he started getting angry and jealous, because Hijikata was getting all of the attention from Kondo and Mitsuba, who started having feelings for Hijikata. Sougo hated Hijikata for stealing away Kondo and Mitsuba. Hijikata didn't technically steal them away, but it felt that way to Sougo. Hijikata had feelings for Mitsuba, too, but he didn't act on them, because being that he lives a life of a killer, it meant he could die at any time easily, and he didn't want to put her through that. Even though Sougo understood this, he still couldn't help but to hate Hijikata.

Sougo, Hijikata and Kondo moved to Edo with a crew of guys who soon became the Shinsengumi, leaving Mitsuba behind, whose health started deteriorating because she hardly ever took care of herself. As a member of the Shinsengumi, 1st Division Captain, to be exact, Sougo always sends his sister money in order to help her pay for her medical needs. Upon her engagement, Mitsuba visited Sougo in Edo to tell him that she's getting married. Sougo didn't know she was coming, so as he was busy threatening to hurt one of the Shinsengumi members, she asked him not to bully the guy, and Sougo immediately went over to bow and apologize to her, something he never does to anyone else. He also speaks to her in a differently than his usual deadpan manner. He speaks very polite and respectful to her, and is more happy-go-lucky and overall cheerful when he's with her. Of course all the Shinsengumi members busy themselves WTFing at this because this is the last thing they'd ever expect to see with Sougo.

Unfortunately, the doctors say Mitsuba doesn't have much longer to live, and even worse is the news of Mitsuba's fiance being a criminal who sells illegally obtained weapons. It is the duty of the Shinsengumi to stop this, of course, however Sougo asks Hijikata to please consider his and Mitsuba's feelings and hold off on handling this criminal, for he wants nothing but for her short time left to be filled with happiness. Hijikata disapproves and plans to take action, pissing Sougo off. Sougo can't help but to again feel as though Hijikata ruins everything, and attempts to attack him, and loses in the end, which never happens, probably having to do with the fact that Sougo's mind was preoccupied with his sister. At the hospital next to his dying sister, Sougo tells Mitsuba that he's realized that everything was actually his fault — her health, her life, all because of his selfishness and wanting things for himself, and wanting things to go his way. He blamed himself for ruining her happiness, but she then said to him that she's happy she got to know him, Hijikata and Kondo. Most of all, she said that she's proud to have had him for a brother, and that he's strong person, to which he admitted he doesn't agree with at all. He just kept apologizing for being a terrible brother, and cried when she soon passed, and still hates Hijikata, even though part of him sorta kinda also considers Hijikata a friend. A complicated love to hate relationship, that's what they have. Still, with Mitsuba gone, Kondo is now the one person Sougo is loyal to, and will do anything to protect him. Before Mitsuba died, Kondo had a talk with Kondo at the hospital, talking to him about Hijikata. Sougo didn't want to hear any of it, of course, and asked him if he is a bother, unlike Hijikata, and said he always feels like he's different from everyone else, like there's a space between him and everyone else even though he's always with them. Kondo punched him in the face and told him that he's always going to be there to make sure Sougo doesn't lose his way, and that he expects Sougo to punch him in the face in return if he ever goes astray, and that he would do the same for Hijikata, because that is the kind of relationship they have. Even though that's the case, Sougo still hates Hijikata, and feels he will hate him forever.

Despite Sougo’s sadistic personality, and his love for tormenting others, he is against doing anything illegal/improper. While he threatens to kill people, he won’t actually do it unless it's within his line of duty. Once there was illegal swordfighting taking place somewhere underground that he knew about, but couldn’t do anything to stop it (which frustrated him) since the person involved in that was part of the government, and it’d cause trouble for the Shinsengumi. There was also a time where one of the Shinsengumi members accidentally killed someone they were actually trying to save within a large group of people, and when Sougo saw what happened, he told him that they should never speak of it, and it’ll be between the two of them. Little did they know that there was a survivor hiding who heard them, but since it was Sougo speaking, it was Sougo that this guy came after for revenge. Sougo gladly took the blame so long as it meant the other Shinsengumi member was safe. It’s also the same thing with Hijikata. As much as he dislikes the guy and threatens to kill him, hurt him, etc, Sougo still fights by him and will protect him, and they’re... kinda friends, in a weird love to hate each other kind of way.