After years of living as a NEET, older brother Takuma, mocked and belittled by his high school girl sister Ruka, snaps and loses control. To contain his rampage, he recruits men through an online bulletin board for forced participation. The gathered men are summoned once a month to Takuma's home on Ruka's ovulation day, where they take turns penetrating her premium pussy. Used like a fleshlight, the beautiful girl endures their brutal gangbang, crying and sobbing as her body is repeatedly invaded, desperately craving sperm to fertilize her egg.