A great game! I love ero games that have the dichotomy of resisting tempation or succumbing to it, leaving it up to the player, and I have always wanted to see AVNs have NTR as one more element, rather than totally absent or as the full focus!
I also love how the NTR "partners" are treated with respect - specially thinking of Owen here. Kai seems cool and treated more antagonisticaly than warranted by MC, I happily lost points with the gf so he got the moe moe kyun he paid for haha
I feel that due to the known aprehensions involving NTR, this game doesn't fully admit or even realize its own vocation, what it is/has to be: this is a game with two protagonists, a guy and a woman, each with their own set of love interests.
In like with that imo you should have a different set of stats display depending on if you are reading a scene from MC's POV, or from his mother's. For him the girl stats, for her the NTR paths stats.
My main gripes I'd say involve day 6, and how cheating on the girlfriend seems to occur no matter what, even if you do resist the temptation. I don't know if an option to avoid the other girls romantically is the right call, but I would at least like variations where you start kissing those girls, but don't go further into sexual acts with them (so, the romance still happens anyways, but wheter to go sexual remains up to the player). Of course, I understand this would require constant extra work going forward, so don't be forced to add it, it's just something I personally would like to have. Maybe it could something for you to go back and add once you have completed the game?
In any case, once more, this is a great project that I'm glad exists, so keep doing your best, even if loud voices disaprove - there's many others, like me, who are happy such a game exists!