tekoki karaoke

An 18+ karaoke game show where contestants compete to win prizes by completing songs without any mistakes. The contestants are given handjobs by a particular AV celebrity with only a small curtain hiding it from view, and must endure them while singing.

Despite the "tekoki" in the tag name, the sex act involved doesn't strictly have to be a handjob; a common variation is "teman karaoke", which involves vaginal fingering.