Yuzuru, who had been living a life immersed in club activities and immune to women after enrolling in a famous all-boarding school known for table tennis, had returned home after a long time. Meanwhile, Yuzuru's sister Ai also came back home due to a marital quarrel. Ai, stressed out, learned during their conversation that Yuzuru was still a virgin and teasingly tried to seduce him as a joke. However, her pubescent and innocent younger brother took it seriously, pounced on his sister's massive breasts…and ended up ejaculating inside her.
