As a result of a combination of his good-natured personality and bad luck, Shiki Orifushi ends up enrolling in St. Lukeman's Academy, a school renowned for its delinquent students.

Before entering the school, Shiki had lived a life far removed from being a delinquent, but at St. Lukeman's, he was an herbivore thrown into a predator's cage.
Shiki was well aware of his situation, but his sense of justice and good-natured personality make him catch the attention of one of the school's numerous gangs of delinquents.

For the next year, Shiki was bullied by the delinquents and lived through hellish days, but one day, he almost bumped into the school's strongest delinquent gal, Karin Kohinata, in front of a vending machine. As a result of this, Shiki's school life changes completely.