HBAD-721 My plain-looking older sister, Mochizuki Fuuka, who seems uninterested in sex but is actually secretly very lustful and has a sexy body

Fuka is always quiet and dresses modestly. She loves intimate things, but she is too shy to bring them up with her boyfriend. So Fuka ends up spending her days alone, often indulging in private pleasures. One day, however, she is accidentally seen by a visiting older relative while she is alone. Unaware of this, Fuka becomes exhausted and falls asleep after her private time…