Rikuto had a new younger brother Ayumu after his father’s remarriage. However, little did he know that Ayumu was actually a girl and it was under her mother’s orders that she pretend to be a boy to him. Every day, his heart beats a little faster around his overly cute brother (sister), while her heart aches in having to hide her true identity from her kind brother.<br /><br />With the arrival of spring, Rikuto and Ayumu begin attending the popular private school Asaoka Academy, with Ayumu dressed up as a girl. As Rikuto becomes friends with his classmates, he notices that they all have something missing. His friend from middle school, Matsuri, has lost sight of what it meant to be a girl. The cool-mannered Mao dresses as a boy even though she is a girl. The extremely shy class rep Kimika wishes to change herself. With Ayumu by his side, he sets out to help them seek out what they are missing.