FNS-189 Frustrated older sister stealth NTR who secretly takes her sister's boyfriend's dick, Rui Shinomiya

Rui, the older sister, has returned to her parents' home after a fight with her live-in boyfriend. She initially planned to stay in her younger sister's room for a while, but her sister has a loving boyfriend and treats her like an intruder. One day, Rui accidentally overhears the sounds of the two having sex, and begins masturbating, using their kisses and moans as her arousal. With her vagina soaking wet, Rui can no longer restrain herself, even though she knows he's her sister's boyfriend...