SORA-441 To protect her young sister Mana from her uncle with abnormal sexual desires, the older sister Kana offers herself as a substitute.

An old man living deep in the mountains… I always looked forward to going there every year because of the great outdoors. However, it turns out that the old man and my mom were paying off debts with their bodies without my little sister knowing… My sister Kana can't understand the situation, but she watches as the old man berates our younger sister Mana with lewd language. Kana wants to save her sister and mother somehow, so she starts accepting the old man's desperately creepy fetish. But gradually, that creepshow… begins to take over Kana's body… more than her sister… more than her mom…