HBAD-721 My sister Mochizuki Fuuka seems simple and uninterested in sex, but she's actually a pervert with a sexy body.

Fuka is always quiet and dresses modestly. She loves naughty things, but is too embarrassed to tell her boyfriend. She masturbates alone every day, but one day, an older relative who came to visit accidentally sees her masturbating. Unaware of this, Fuka gets so exhausted from masturbating that she falls asleep...