While left alone to watch the house during her friends' trip, Ruri finds a pink vibrator she suspects belongs to her friend. Overcome with forbidden excitement and a sense of taboo, she gives in to her uncontrollable urges and presses it between her legs. A boy peeping through the window is captivated by the alluring sight of a woman experiencing pleasure for the first time, becoming shockingly aroused himself. Drawn to her sensual form, the boy takes a bold step and asks Ruri to teach him.