Game goes off the rails with the NTR stuff and continuity breaks down at that point. In my game, Sunny had no relationship with Marcus at all but is suddenly going on about how important he is to her. Also, MC turn into a total beta when it happens, not enjoyable at all. When Emma and Marcus start messing around in the bed, MC should have stood up, said something like "Are you two f_ing kidding me?" then just left. When he caught them in the library. he should have barged in and told them both to F_k off and never speak to him again. And so on.
But that's just my opinion.