Office S Partner: Joon-yeong happens to know that Yeon-ji is a virgin. He uses his junior Joo-won to break down Yeon-ji's air conditioner outdoor unit to seduce her. Yeon-ji and Mi-ho, who are tired of the heat, stay at Joon-yeong's house. The four of them are living together! Joon-yeong tries to seduce Yeon-ji, but every decisive moment, Mi-ho and Joo-won interfere. One day, Joon-yeong and Mi-ho go out and they are left alone. Joo-won enters her room to a virgin Yeon-ji...