I think I found an inconsistency (2 actually), as it doesn't seem intentional:
When playing the sex scene with Nicole and Alice, MC is given the option to let them kiss freely
or only when he's present.
If the 1st option is chosen, it is also possible to later encourage Leana and Tiffany to kiss as well (if he checks up on them, instead of Alice)
If the 2nd option is chosen, he can still visit them both
but he won't encourage them to reconcile with a kiss
So during the Alice and Nicole scene, I picked the 2nd option... and Later on I missed the kissing option between Leana and Tiffany, which doesn't make sense to me really. Since firstly, MC shouldn't have a problem with girls kissing in his presence (as that's what he also says to Nicole and Alice in the 2nd option), but also because this is a different instance involving different girls.. I kinda wish it wouldn't depend on that, as I still wanted to encourage them
The other inconsistency stems from this issue further along the story - when Tiffany wants to say goodbye to Marc in the bathroom. He can ask her for a kiss as well, and although I did check on Tiffany and Leana and made them reconcile, I didn't make them kiss (since I didn't get the option). Despite that, Marc still refers to a kiss between Tiffany and Leana, although it never happens in this set of choices.

(He tells Tiffany: "I remember how she smiled when you two kissed")