Wada is [Satomi's](https://anilist.co/character/357110/Satomi-Oka) junior in the choir club. 

The president of the chorus club, Satomi Oka, is approached by a yakuza named Kyoji Narita. Kyoji’s yakuza group holds a customary karaoke competition, and whoever earns the title of worst singer must get a tattoo. Since he was asked to be Kyoji’s singing teacher, Satomi has no choice but to go along with these practice sessions. Brought together by karaoke, where will Satomi and Kyoji end up?<br>
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(Source: Crunchyroll)

Nothing worries Satomi Oka more than the upcoming final choir competition of his middle school career -- right up until he is accosted by a stranger from the shadows who demands, “Let’s go karaoke!” As a yakuza, Kyouji Narita doesn’t scare easily, but a terrifying prospect has driven him to seek Satomi’s help. The boss is holding a karaoke contest, with the loser forced to get a tattoo to be selected and torturously applied by the boss himself! Oka has been to many vocal rehearsals over the years, but never one-on-one karaoke sessions with a gangster!!
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(Source: Yen Press)