Rui, who had returned to her parents' home due to a fight with the boyfriend she was living with. She planned to stay in her sister's room for a while, but her sister has a boyfriend she's head over heels for and treats Rui like an intruder. One day, Rui accidentally hears the two having sex and starts masturbating using their kissing and moaning sounds as stimulation. Wet her cunt, can't hold back anymore. Even knowing he's your sister's man, greed gets in the way and you can't help but reach out for his dick...
