Satomi Oka's main concern for his middle school choir is the upcoming final competition, but this changes when a mysterious stranger, Kyouji Narita, approaches him with a demand to go to karaoke. Narita, a yakuza, needs Satomi's help to participate in a karaoke contest organized by their boss, where the loser will be forced to get a tattoo applied by the boss himself. This unusual situation involves one-on-one karaoke sessions with Narita, who has a lot at stake in the competition.