Kagami Seiichiro was an inconspicuous and introverted male high school student. But one day, he stumbles upon a scene where the most beautiful girl in the class, Kamiyo Karen, is confronting a debt collector.
Seiichiro, who had been making a large amount of money through special circumstances (and a genius-level talent for gambling), ends up taking on her debt in the heat of the moment.
Seiichiro, who had fallen into mistrust of others due to his past experiences, had no intention of getting involved with Karen, even though he had helped her. However, she barges into his house where he lives alone, pleading, “Please let me repay the favor!”
Furthermore, he ends up living with Karen’s beloved younger sister, Kamiyo Erika, as well.
The story begins with the most beautiful girl in school and a middle school girl with a model-like figure moving in to help with housework in the home of a boy who, due to his genius gambling talent, has gained a fortune at the cost of losing his family and lives alone—a slightly immoral romantic comedy.