Let's Go Karaoke!

Satomi Oka, the captain of his school’s choir club, is suddenly approached by a yakuza member named Kyouji Narita. His request is unexpected: “Let’s go karaoke!”
In Narita’s group, there is a rule that whoever scores the lowest in their karaoke contest is forced to receive an awkward tattoo from the boss
Desperate to avoid this fate, Kyouji begs Satomi for vocal training, and Satomi reluctantly agrees to help him practice.
What will become of this strange connection formed between the two through karaoke?