Moments before her upperclassman, Yoshihiko, left for college, Kana Orikura finally built up the courage to confess her love to him. Sharing their first kiss, the two decided to enter a relationship—a dream come true for Kana. Since that first moment, however, Kana and Yoshihiko have struggled with their relationship, resulting in Kana feeling lonely and depressed. But things take an unexpected turn when Shougo Hayakawa—the young and attractive teacher assigned to Kana's class—starts living in her house! Will Kana betray Yoshihiko for this new contender, or remain loyal to the man who took her first kiss?