u/Notationsfehler

Lookin for Doujin, that starts with the MC and his (I suppose) girlfriend are fighting (more like fooling around) with each other. She ist stronger than him, so the consider having sex to "fight" with each other again. Afterwards the mother of the girlfriend takes the MC to a restaurant, where she blows him under the table. They then get into a karaokebar and have sex there - the girlfriend discoveres the two having sex in the bar at the end of the doujin.
Not sure, might be a multi-series work.