My sister "Minori" had been afflicted by a certain illness that made her sexual desire uncontrollable. Once it takes hold, she becomes aroused anytime, anywhere, with anyone. Feeling pity for my sister in this state, I made the decision to isolate her in a unit bath. After struggling with her constant craving for a man's penis, I resolved to keep having sex with her. She reaches orgasm easily with just a touch, finds pleasure in having her throat deeply penetrated, and repeatedly demands sperm in her womb. For my sister's sake, I continue to have unprotected creampie sex with her every day.