Natsuo is a third-time college entrance exam retaker who is no match for his older brother Masaki in terms of looks or academic background. The dull Natsuo secretly has a crush on Masaki's girlfriend Manami, without his brother's knowledge. One day, Masaki arranges for Manami to be his tutor, and Natsuo is overjoyed... But just then, he learns that Masaki and Manami are engaged. In Kokoro, he wants to congratulate the couple on their happiness, but when he hears Manami's moans coming from his brother's room, his lewd fantasies grow...