Kyō Nukui is a shut-in high schooler with a love for music, often posting his music online under the fake name of HibikiP. One day, an anonymous sender wants to meet him at a park, to which Kyō agrees, thinking it to be a middle-aged man interested in discussing music like him. However, the anonymous sender turns out to be three elementary school girls Jūn Goto, Nozomi Momijidani, and Sora Kaneshiro, who request that he play his music with their band in an upcoming concert. They perform first for him, and despite being highly impressed with their musical skills and vintage instruments, is still unsure about his decision.
Kyō agrees to help the girls with the concert, but Masayoshi Sawatari, the head of the orphanage where they live, asks him to dissuade them.
Kyō discovers that Jun and the others are classmates of his younger sister Kurumi, but for some reason do not get along well with the other kids at school. He also finds out that his childhood friend Sakura Toriumi is also an orphan from Little Wing, and asks him to keep it a secret.
Kyō and the girls have no success at all to gather attendants to the concert, and he then decides to return to school and ask for his classmates' help, while suggesting the girls to do the same at theirs.
The concert is a success, and Kyō and the girls' next step is to gather more public to make a steady income from their gigs. By suggestion of a friend, Kyō decides to make a PV of them for advertising.
Nozomi meets her grandfather, who wants to adopt her and take her to England. Kyō and the others decide to not ask her to stay in order to not influence her decision, until Kyō's sister Kurumi gives him a piece of her mind.
Kyō is invited along the girls of Lien de Famille by his online friend Yuzuha Aigae to hold a concert on a resort island, unaware of her true intentions.
Uneasy with Kyō's closeness with the girls, Yuzuha comes with several ploys against them, just to be exposed by Sakura. When a storm approaches the island, Yuzuha disappears and after finding her, Kyō discovers her secret.
Kyō discovers that his online friend was not Yuzuha, but Kiryu Yume, and Yuzuha was acting in her stead. When Kiryu decides to cease all connections with Kyō and the others, they decide to find a way to cheer her up.
Kiryu and Yuzuha gain permission to leave the island and transfer to the local school. While helping Yuzuha around the city, Kyō ends up spending some quality time with her, triggering the other girls' jealousy.
Enraged with how much time Kyō spends with the girls of Lien de Famille, Kiryu decides to form her own act with Yuzuha and Kurumi's help and challenge them to a duel. In the occasion, Jun expresses her wish to write a music of her own, and Kyō agrees to help her with it.
After finishing their preparations, the time has come for Lien de Famille and Kiryu's band to perform together.