Hatanaka Kosaku has enormous potential as a boxer with his devastating knockout punch, but his lack of self-control is a hindrance to his career. Despite being aware of the importance of maintaining a healthy diet, he regularly indulges in greasy burgers before fights, causing him to be unable to compete in his desired weight class. Just one blow to his abdomen leads to vomiting, resulting in his loss of matches and a sense of shame. Struggling with his discipline, Hatanaka encounters Sister Angela, a novice nun in a nearby convent. Although Sister Angela is genuinely eager to support Hatanaka, his presence and habits inadvertently challenge her religious training.