Atsuya takes advantage of his summer vacation to visit his aunt Mizuki's house for the first time in a long while. He can't look directly at Mizuki's voluptuous body, which is different from how he remembers it from his childhood. Mizuki finds his innocent reaction amusing and teases Atsuya repeatedly... But that night, he accidentally peeks at his aunt and uncle's lovemaking. The next morning, Atsuya blushes as he remembers what happened last night, and Mizuki presses him, asking, "You were watching yesterday, weren't you?"