While tidying up the Calligraphy Club room, Kiryuu Keiki stumbles upon a surprising love letter addressed to him. Hopeful for a romantic connection, he unveils the message 'I like you' accompanied by a peculiar gift—undergarments. Armed with this unconventional clue, Keiki identifies four potential suspects: the apathetic senior club president Sayuki Tokihara, the foreign library committee member Yuika Koga, the slightly aloof classmate Nanjou Mao, and the fastidious younger sister Kiryuu Mizuha. Certain that one of these atypical girls holds the key to his heart, Keiki embarks on a quest to reveal the true sender and potentially find his future girlfriend amidst this eccentric bunch!