Monstar

First day of school, K-pop boy band leader Seol-chan asks New Zealand girl Se-yi to be his partner.

Seol-Chan, Se-Yi and Seonu, the class president, prepare for the music performance evaluation, but find themselves in big trouble when Seol-Chan forgets all about the evaluation on the test day.

Seol-Chan witnesses Se-Yi and Seonu singing together and feels a twang of envy from their duo; the second year class goes to Gyeongbok Palace to become entangled in an unimaginable event.

Seonu claims his affection for Se-yi and Seol-Chan is left without options; the band comes together in an attempt to solve the problem at hand, but fails to work together due to their emotional discrepancies.

Seol-Chan succeeds in bringing out Do-nam's skill to be able to complete the concert; the All-for-one band proclaims to rejoin the concert, giving no choice but for Seol-Chan to propose a battle-of-the-bands against the All-for-one band.

Seol-Chan continues to be jealous of Se-Yi and Seonu's relationship, and expresses his anger towards Se-Yi, disregarding the practice that is going on for the battle-of-the-bands.

Seol-Chan becomes aware that the rival band has an excellent vocalist, leading him to carry out excessive practice sessions; Se-Yi storms out of the room and the battle-of-the-bands continues to look hopeless for the team.

After defeating the All-for-one band, The Kallaba band attracts attention from neighboring schools; Se-Yi and Seonu's relationship continues to break down due to an interruption from a jealous one.

The Kallaba band members are shocked by what happened to Gyu-dong, while Do-nam blames himself for this situation; Seonu asks Se-Yi out which makes the trio relationship even more awkward.

Seol-Chan shares his first kiss with Se-Yi but is unable to ask her out; Seol-Chan throws himself to protect Se-yi in gym class and goes to the infirmary; Eun-Ha spots Se-yi and Seol-chan together in dismay.

Seol-Chan and Se-Yi confirm their feelings towards each other, but are unable to disregard Seonu from their relationship, making things awkward again; an unexpected offer is given to the Kallaba band.

Se-Yi informs Seonu about her feelings for Seol-Chan which breaks his heart; the Kallaba members prepare for their final battle against the All-for-one, when PD Byeon learns the secret behind Se-yi.