JUFE-101 A defenseless big-breasted sister gets fucked by her super-obsessed younger brother. She thought she was trying to seduce her virgin brother, but... it turns out to be a complete reversal! Ai Sayama

Yuzuru, who enrolled in a prestigious boarding school famous for table tennis and was living a life immersed in club activities with no immunity to women, returns to his parents' home for the first time in a while. Meanwhile, Yuzuru's older sister Ai returns to her parents' house after a quarrel with her husband. During a conversation, Ai, who was under stress, learns that Yuzuru is still a virgin and tries to seduce her and make fun of her, but the adolescent Makoto takes it seriously.