A young man named Hatanaka Kosaku is an aspiring boxer who possesses a powerful knockout punch. However, despite his strong physical abilities, he struggles with maintaining discipline and making healthy dietary choices. This leads him to compete in heavier weight classes, where even the slightest abdominal blow can cause him to vomit and lose the match. As he grapples with his self-control issues, he encounters Sister Angela, a novice nun at a nearby convent. Although she tries to assist him in improving his boxing skills, Hatanaka's behavior seems to make her training more challenging.