Bro, you are looking to this situation as an outsider, i wont say there isnt some mistake here and there, nobody is perfect, but think this as Mc, he is a guy that dedicate his life to the sport, never a date, never mess around, he was obsesive with winning, so now that he lost that, is not suprising that he cant control himself and even more important that he doesnt know the consequences of his action, to him, this is a new experience, so he just losing control, but believe me it will have consequences, even if the Dev decide to make it a harem, it wont come easy, we have already see that the dev isnt afraid of hurting his Mc.
Another thing that i want to explain is that he isnt the only one with social difficulties, let think about the girls he has had something, Lexi is an open girl, i am pretty sure she wont have an issue with the Mc messing around with other girls but with how much of a sore loser she is she will try to make him choose her as her favorite, Saki is weird so even if it bothers her, she would try harder to make him fall for her, i dont see her fighting for him since she has such a inferiority complex, and Eve is the only one i see having a problem with it, but she is a pretty emotional girl, right now i dont see
how the problem Can be resolve, but she still can be convinced, of that i am sure, thats how good lopaphi writing is.
So yeah, i understand your point and this is an issue that cant be resolve yet, but depending on how lopaphi resolve the problem, it can be saved, let the man cook.