Season 1

Tae Yi meets Se Heon in the music classroom, where he gives Se Heon a stern warning.

After a confrontation, Tae Yi decides to take Se Heon seriously, but it also brings back memories of his past.

Joo Ha invites Se Heon to sing at a karaoke bar, and his actions towards Se Heon anger Tae Yi.

An accidental kiss leads to a confrontation between Joo Ha and Do Yoon. Tae Yi unexpectedly faints at school which raises Se Heon's concerns.

A performance brings Tae YI and Se Heon closer together while the distance between Se Heon and his father grows deeper.

Tae Yi takes in Se Heon, who has run away from home, and Tae Yi's gestures begin to emotionally affect Se Heon.

The song that Tae Yi plays leads to a secret being revealed about Se Heon's brother.

Tae Yi encounters Se Heon's brother, and the encounter reveals the story of the song.