After 15 years of seclusion, 30-year-old virgin Shintarou Koizumi strikes a deal with his father: if his father finds love, Shintarou will emerge from his room. Little did he know that his father already had a girlfriend, the captivating Haruka Yoshinaga, who had her own motives. Following Yasujirou's sudden passing, Haruka steps in to care for Shintarou, creating an unusual bond between them as a peculiar 'mother and son' duo under one roof.