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.

A photo of Yuu and Koyuki taken outside his home spreads like wildfire on Twitter, creating a huge scandal for the popular singer. Even Yuu's account is found and targeted, and wild rumors are going around at school. The band's practices in preparation for the school fair had been coming along smoothly, but the rumors spoil Fuuka's mood. Meanwhile, Koyuki addresses the controversy on national television with a surprising declaration.

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.

For their first date, Yuu and Koyuki meet to visit a small town that she once visited when filming for a variety show. Meanwhile Yuu's band, The Fallen Moon, has been selected as an opening act for a gig at a live music club. Fuuka suggests they write an original song to play there, but a strange sense of confusion in her heart makes the process difficult.

Fuuka continues to struggle with the lyrics for the band's original song. A concerned Mikasa tries to reach out, but Fuuka is unable to verbalize her true feelings. Yuu also becomes worried and calls her, but his kindness only makes her feel worse. With their first gig only days away, what feelings will Fuuka express in her lyrics?

Fuuka's sudden decision to quit the band and go solo shook the members of The Fallen Moon. They had successfully completed their first gig and were determined to make their own legend, but they can't be a band without a vocalist. Despite their lingering regrets, Sara, Mikasa, and Nachi set off to walk their own path.