This isn't some stupid romcom.
If the two of them want to fuck, they would just fuck. Personal baggage be damned.
You're 165 chapters in, how do you not understand this by now?
Remember the needle girl was out here getting raped day in day out repeatedly in the afterlife before they showed up on the flying ship and there was no quarrel whatsoever.
If you're actually pissed off about characters having sexual affairs without Kazuya then you should have dropped this manga a long long time ago.
