I Happened Upon My Girlfriend’s Little Sister As She Came Out Of The Bathtub, And There She Was, Without Her Bra On, And I Couldn’t Control My Erection – Hikari Aozora

Plot: This guy lives with his girlfriend in Tokyo. One day of summer, her younger sister Hikari comes to stay over and she messes everything up like a tornado. This schoolgirl despite looking innocent, she is extremely lewd and has stamina for years.