18+ Hidan no Aria

Tokyo Butei High School is a place where teenagers are trained to be "Butei," combat detectives. Tokyou Butei student Touyama Kinji, who is otherwise ordinary, has a special ability to go into "Hysteria Mode" that can trigger without his control when he is in close proximity to girls. In his Hysteria Mode, which he is trying to keep something of a secret, he becomes super powerful and very concerned with protecting women. One day Kinji is targeted by a Butei killer, who rigs his bicycle to explode, and is rescued by assault expert transfer student Aria H. Kanzaki. But after witnessing his Hysteria Mode, Aria will not leave him alone...

(Source: MU)