Japanese teenager Luka and Korean trainee Sungjoon share a powerful dream of debuting together as idols. Through a project run by one of the biggest entertainment agencies in the K-pop industry, the two are promised spots as members of a new boy group. However, just before their debut, Sungjoon suddenly vanishes from Luka's life without explanation. Two years pass, and Luka finally debuts as a member of the group CIIEL. During a performance, he hears the main vocalist of a rival group called MTTS, a young man named Juno. While Juno is clearly a different person in appearance, his voice is unmistakably the voice of Sungjoon. The story follows Luka's shock and determination as he confronts this impossible situation, with the dark realities of the entertainment industry threatening to completely tear apart the pure promise the two young men once made to each other.