Chika has a younger boyfriend (Yuta) and has been invited over to Yuta's house today. Yuta has an older brother (Ippei) who lives with him, but he's away on a business trip, so they can have sex to their heart's content! However, Yuta ejaculates without fully satisfying Chika. Unable to climax, Chika even masturbates with a vibrator while Yuta is in the shower. Ippei, who has suddenly returned home, peeks into the scene. Yuta leaves Chika asleep after masturbating and goes to work. Ippei, jealous of his brother's girlfriend Chika's eroticism, invites his seniors and friends over to his house to try out an aphrodisiac he has always wanted to use...