The introverted Yuu Haruna has moved to Tokyo to live with his three sisters. While passing through the local shopping district, Yuu has a chance encounter with Fuuka Akitsuki, and things get off to a rough start.

Yuu spots Fuuka in the hall and is about to talk to her, but then notices she's crying. He follows her eyes and sees that she seems to be looking at their classmate, Mikasa. After school, Yuu ends up on pool-cleaning duty with Fuuka and Mikasa.

"We're starting a band!" Yuu's casually spoken words gave Fuuka the idea to start a band. Yuu and Mikasa are dragged into the plan, and the three of them start a light music association.

The sight of Yuu on the beach at night with Koyuki is such a shock to Fuuka that she runs away. Yuu tries to make up for it by explaining that he and Koyuki were friends as kids, but that angers Fuuka even more.

The new school term has begun, and Yuu's band has begun to practice in earnest. They have one of their idols, Hisashi of HEDGEHOGS, teaching them how to play their instruments, but bassist Yuu and vocalist/guitarist Fuuka are complete beginners.

Koyuki makes up her mind to face Yuu. She visits his home to give him concert tickets. Then Koyuki runs into Fuuka on her way home, and somehow the two of them end up in a bathhouse together.