Hidan no Aria

Tokyo Butei High School - a special school where armed detectives, also known as "Butei" are trained. Tohyama Kinji is a sophomore student who has a unique body which activates a "super mode" when stimulated by "something." He tries to hide it from others in order to live a peaceful life. But trouble finds him when he becomes a victim of a bombing incident, where he meets the Butei High "Assault" department elite, Aria H. Kanzaki. ___ (https://www.animenewsnetwork.com/encyclopedia/anime.php?id=11451)