The story focuses on Kenichi Shirahama, an average 16-year-old weakling, whose life is upended with the appearance of the naive, beautiful, and strong transfer student, Miu Fūrinji. After Kenichi witnesses Miu's skills in martial arts, he joins the Ryōzanpaku dojo, a gathering place of those who are truly strong, which coincidentally also happens to be Miu's home. After beating a karate student in a match, he is soon targeted by all the delinquents in the school. Since then, Kenichi's daily routine is divided between his hellish training with the six masters of Ryōzanpaku, and his fights against the members of Ragnarok, a gang who views him as either a possible ally or an impending threat to their plans.
兼一是個善良的高中生,但總受到許多不合理的欺負,他在偶然的情況下,與轉學生風林寺美羽成了好朋友。之後受到美羽的吸引之下,到了名為「梁山泊」的道場修行武術。