Morioka Middle School's choir may have finished second in a national contest, but 39-year-old yakuza Kyouji Narita considers them the finest. His criminal family's boss is fond of karaoke and tattoos, combining these interests by compelling every member to compete in a singing duel; the loser receives a hand-pricked tattoo selected by the boss. Since the boss is a total amateur, Kyouji is anxious to avoid becoming his next subject. To learn how to outperform the others, Kyouji turns to 14-year-old Satomi Oka, the leader of Morioka's choir. Satomi finds little logic in Kyouji's situation or the absurd competition; he is preoccupied with his own issues, navigating puberty and a changing voice that appears to fail him more frequently each day. Yet, feeling a bit of sympathy for Kyouji, Satomi tentatively starts training him, attempting to understand his uncertain adolescence and his new, unconventional friendship with a gangster.