I doubt there will be any real ntr in the story. It would be a weird turn considering how pretty much all females view mc as the hottest/best guy in the universe.Question is will Dev touch on NTR in the story as hes kinda avoided any rivaly from other men to MC
And mc's dad shouldn't be much of problem since I doubt his wife would ditch him for her son otherwise. The first thing that come to mind in case mc's dad being the one who impregnated Hiroko is that he at one moment witnessed his wife "taking care" of mc and out of frustration/desperation raped Hiroko (who maybe came to visit mc at that time) after which begged/threatened her to keep this secret because otherwise mc's life would be ruined due to scandal.