I can't believe my mom makes that kind of noise... The lewd cries of his mother, Natsumi, echo from his parents' bedroom as they plan to have a child. When Keita learns of this previously unknown side of Natsumi as a woman, emotions well up within him that he cannot suppress. They are Kokoro towards his father, who is thrusting his penis into his mother's body. Kokoro towards the sibling he has yet to meet, who will likely monopolize his mother's love. Mom is mine. I don't want to give her to anyone else... Keita enacts a plan to monopolize his mother's love. That is to overwrite the sperm of his father that had been injected into Natsumi's uterus with his own sperm...