Kenichi Shirahama, a perpetually bullied high schooler, follows new classmate Miu Fūrinji to Ryōzanpaku, a hidden dojo where six masters of different martial arts — karate, muay thai, jujitsu, Chinese kenpo, weapons, and judo — live under one roof. Their training nearly kills him daily, but each ordeal pushes the self-proclaimed weakest disciple closer to actual competence. As Kenichi's rapid improvement draws the attention of Ragnarok, a street-fighting syndicate that controls the area's delinquents, the fights shift from the dojo floor to the real world.