Hatanaka Kosaku, a hopeful boxer, has a mean KO punch. Unfortunately, his dietary willpower is weak, and he eats even greasy hamburgers right before a bout. As a result, he has to compete in higher weight classes, and as soon as he takes an abdominal punch, he vomits, which causes him to lose the match in shame. As he tries to grapple with his weak will, he meets Sister Angela, a novitiate at a local convent. While Sister Angela strives to help Hatanaka in his endeavor, he seems to make her training to be a nun more difficult.