Morioka Middle School's choir may have placed second in a national competition, but 39-year-old yakuza Kyouji Narita has judged them the best. The boss of his criminal family loves karaoke and tattoos—and he blends his hobbies by forcing every family member into a karaoke showdown, the loser receiving a hand-pricked tattoo of the boss' choosing. However, the boss is a complete amateur, and Kyouji is desperate to avoid becoming his next canvas.

To learn how to outsing everyone else, Kyouji seeks help from 14-year-old Satomi Oka, the head of Morioka's choir. Satomi sees little reason in Kyouji's actions and the ridiculous competition; he has his own worries, being in the middle of puberty and dealing with a changing voice that seems to betray him more each day. But feeling somewhat sorry for Kyouji, Satomi cautiously begins coaching him, trying to make sense of his uncertain teenage years and his new, offbeat friendship with a gangster.