More jealous bfs cause why not. Ship suggestions are:

-Kawaniwa (Moniwa/Kamasaki)
-Daisuga
-Levyaku
-Bokuaka
-Iwaoi
-Arankita
-Sakuatsu

So their partner is being talking to by someone. Said partner is completely unaware that they are being flirted with. They noticed and come over, hiding how they feel, and wrap their arm around their shoulder and say something along the lines 'Hey baby what's up?' and kiss their cheek. There is various reactions (Some are flustered, some are confused and some are used to it) Said person who was flirting with them now realize they're taken and leaves 'Hey where did --- go?' 'Doesn't matter' and kiss them on the mouth this time