It's a little too early to rate this, and there are lots of improvements that could be made to turn this into a "5" and here are a few suggestions:
Most importantly, get a native English speaker with some skill to edit the text. It is perfectly understandable at this point but the lack of and misuse of articles (the, a, an) is a little jarring and many of your potential audience may be put off by that or other minor grammatical errors.
You've already run across the ntr controversy. Regardless of how you proceed, you will hear complaints from one or both of the opposing sides. Unavoidable NTR will kill a lot of interest in the game, particularly if it is netorare or netorase (almost nobody complains about netori so don't worry about that {and you already have your protagonist messing around with another man's wife}). Avoiding ntr (keeping your foster family away from the fate that awaits them) is a major part of the motivation for your MC, so I'm not sure about a "remove NTR" button at the start simply because it removes an important part of the plot. Be true to your own vision of the story you want to tell, in the long run you'll end up with a better story and more supporters. There will be many comments from people who want you to twist your story to meet their standards. Try to please everyone and you end up pleasing no-one, not even yourself. And the people you try to please will just go on to make another 20 posts on some other forum to try and persuade the creator to tell the story they want (again and again and again).
Ditch the overuse of black screens to transition between scenes. You can indicate the passage of time by simply adding a time or place reference ("Later at school") to the next dialogue box or drop in an eye candy shot of one of the LI's as a transition screen (you can even make the screens progressively spicier as you build points with the LI's).
You have a lot of plot elements to juggle (warring Yakuza, competitive demons, secret masters of the mystic arts, high school shenanigans, a missing artifact, revenge for your dead father and seeking your missing mother) all of which make me want to continue with this story. I think that's enough, so don't try to overcomplicate things more at this point.
For real romance we need more of a backstory for the LI's. Something that makes them more vulnerable and stirs the protective interest of the MC (as an extension of the reader). You don't have to write a novel, but a couple of short interchanges where the women reveal hopes, fears, and insecurities will help. A good harem requires not only a reason for you to fall in love with the girls, but a reason for the girls to fall in love with you (and to be accepting of the other members of the harem). The MC isn't the only one who is making decisions here, there should be some quality (beyond a magic dick) that brings the girls to him: something they need that he can provide. They may have originally felt pity for him, but the two month break, the new physical presence, and his new assertiveness and masculinity make him much more attractive. The more we know why they need him, the more easily the romance flows.
Beware the temptation to make your MC a Gary Stu character. It should not be a walkover. Your MC should face real challenges that he needs to overcome, either by himself or with the aid of his allies. Let him develop his powers over time and with some effort on his part (but avoid mindless grind, if he needs five sessions to gain a martial arts skill try to have a progression of renders and different dialogue to keep the readers interest and reduce complaints).
When using tropes (truck-kun), make them ironic or twist them slightly so the audience shares the joke (perhaps make it ambulance-kun instead). Don't break the fourth wall too often, if at all, because that shatters the immersion for the reader.
You've got great material to work with here, your models are attractive with realistic bodies, and your renders and animations are ok at the moment (as time goes by they'll probably improve). All in all, you've made a great start and I hope you succeed. I'll probably review after a few more updates and I hope I can give a "5".