Admiring idol HAYATO’s songs, Nanami Haruka decides to enroll a musical school, Saotome Academy, in order to become a composer and write songs just like HAYATO’s.
As she’s late for her first day at school, Haruka stumbles and falls in front of everyone, gaining the attention of six young men from the idol course. Later that day, Ittoki Otoya approaches her and asks her whether she’s hurt after falling at the opening ceremony and Masato Hijirikawa joins him giving her the tissue she dropped earlier. Natsuki then jumps in saying she’s cute but is interrupted when Class A’s homeroom teacher, Tsukimiya Ringo, enters the classroom. He gives them a brief introduction of the school and after that asks everyone to introduce themselves. As Otoya, Masato and Natsuki introduce themselves, Haruka is stunned by their handsomeness and wishes to make a great song for all of them that would make everyone happy. When Ringo tells her to introduce herself, she stumbles again but is encouraged by the trio. Ringo afterwards introduces “the red string of fate” system of finding their partner with whom they will be working with while they’re students at the academy, but tells them that relationships are absolutely forbidden. When they’re about to reveal their partners, a black cat jumps in and messes the strings up, making the students choose their string ends again. When they reveal which one belongs to who, Haruka ends up being paired with the handsome trio – Otoya, Masato and Natsuki.
That night, Haruka meets her roommate, Tomochika Shibuya, who tells her that the guys who she’s paired with are sharing their rooms with guys from Class S, their rivals.
The next morning, the Class S and Class A have a joint class together where they compete against each other in groups of three. Otoya, Masato and Natsuki pair up while Tokiya, Ren and Syo from Class S pair up and at the end, those two groups end up being the last ones still standing. With Class A winning over Class S in the game, Shining Saotome gives the group their revard, which is a melon bread with “Proof of an Idol” written over it and the group decides to give it to Haruka since she’s the one they can’t sing without. She refuses, however, and decides to share it with them because, without them, her songs can’t be heard.