Profile

Before the start of the series, Kohta went on a month-long trip to America where he was trained by the US military contractor Blackwater USA which furthered his obsession over weapons. When Kohta attended school he was constantly bullied by classmates in Koichi Shido's classes where instead of helping Kohta out, Shido encouraged the bullying. This led to Kohta holding in feelings of frustration and anger towards Shido.

Before the outbreak, Kohta's demeanor is one that is timid, carefree, and sanguine. Yet at the same time, in constant suppression of his frustations due to the frequent bullying that he suffers from school, all for the sake of having a "normal" life.

As a result, when "they" started to emerge, Kohta was one of the few people who readily accepted to the change needed to ensure his and his comrades' survival, finally being able to unleash all the frustations that he has accumulated so far. And while normally capable of maintaining a cool and level-headed demeanor (more so than Saya), Kohta has exhibited a sadistic and almost maniacal side of himself, to the point where he actually displays a slasher-style smile that shows whenever he kills "them" in cold blood. Saya once mentioned that Kohta and Takashi are the most likely to snap if things keep going the way they are. He has grown very attached to Alice Maresato and can often be found playing with her.

http://highschool-of-the-dead.wikia.com/wiki/Kohta_Hirano