The introverted Yuu Haruna has moved to Tokyo to live with this three sisters after their parents left to work abroad. While passing through the local shopping district, Yuu's eyes are riveted on a TV screen in a store window when a girl comes running up the street and crashes into him. That is how he met the girl who seemed to be wrapped in a summer breeze: Fuuka Akitsuki. Their first meeting goes downhill when Fuuka mistakes Yuu's intentions with the smartphone in his hand, and on top of that, he then finds out that they'll be in the same class at his new school...

Yuu ends up on pool-cleaning duty with fellow classmates Fuuka and Mikasa, who seem like more than just friends. Meanwhile, Koyuki Hinashi, a popular singer who was childhood friends with Yuu, calls him for the first time in years.

Yuu and Mikasa are dragged into Fuuka's plan to form a band after Yuu unwittingly gives her the idea, and the three of them start a light music association. In order to earn money to afford their instruments they decide to stay at a beach house over the summer and work part-time. But the personality of the owner, Yahagi, rubs Yuu the wrong way.

Yuu's late night meeting with Koyuki causes misunderstandings between him and Fuuka. Yuu's attempt to make up fails, and the mood remains awkward between them at work. Meanwhile their teacher, Tomomi, shows up at the beach house with the track team captain, Nachi, and reveals something unexpected.

The new school term has begun, and Yuu's band has begun to practice in earnest, but bassist Yuu and vocalist/guitarist Fuuka are complete beginners. Nachi isn't much better as a drummer, and they attempt to recruit a senpai from their school, Sara Iwami, to take over on guitar. She's cold to them at first, but a revelation about Yuu brings her around.

Memories of childhood, parting, and regret cause Koyuki to make up her mind to face Yuu. She visits his home to give him concert tickets, but the two of them had no idea that this meeting would have immense consequences... On her way home, Koyuki runs into Fuuka, a huge fan of the singer, and the two end up at a public bathhouse together, much to Fuuka's delight.

The day of the school fair has arrived. Fans enraged by Yuu and Koyuki's scandal crowd around and shout abuse as their band takes the stage. Yuu is certain that the power of Fuuka's singing can silence them, but chaos breaks loose. Koyuki, who had come to see Yuu's concert in secret, can't stand silently by any longer.

Yuu writes an original song in an attempt to bring Fuuka back to the band, but she avoids him completely. Now, as their growing popularity online has earned the attention of the HEDGEHOGS members, they've been invited to play at a live club again. The members have no choice but to practice their new song with no vocalist, but Yuu still isn't willing to give up.