Murder Lock: Satsujinki no Kyoushitsu

Kotaro Kuoto is a high school student known for his strength and his close relationship with his sister, Hinami. After several men who had previously taken Hinami are discovered dead, Kotaro is arrested and accused of their murders. Despite claiming innocence, he is sent to a school for underage murderers who were accepted based on specific criteria. At this institution, he encounters other young students with violent tendencies and a staff of eccentric teachers.