I'm surprised that the near ntr by another girl (even if nothing was going to happen) just got swept under the rug. Considering MC's trust with women problems, I can see why this is the case, but if it's found out later then the damage in trust will be exponentially worse.
I could see mc being forgiving considering how he is in to much of a mess to understand his worth, but consider the fact that Meltina just proved that a convincing enough illusion was enough to fool her teenage brain, and you got yourself a good bit of character development to work through before she could be worthy of a second chance.
That or she could just form a slave contract with MC so she never betrays him again if the author doesn't want to go down that rabbit hole, but that would raise the question if MC can even stomach something so inhumane considering his former Japanese upbringing...