not quite sure after going through all the translated chapters. The second group of kids keep getting the misunderstanding that him and the eldest girl are sleeping together (sexually) because all of the first group of kids sleep on his bed. She doesn't bother to clear up the misunderstanding and gives a little undirected apology to his ex gf (the swordswoman) because she thinks he only sees her as a daughter 'for now'. On top of that, the wn specifically says she's only 13. It's been purely wholesomeness (and violence) on his part and he and the kids have a very good relationship with his ex, so I wish the story wouldn't creep stuff like this in.
You know that this is a common female self-insert fantasy though? Stuff like usagi dropped and that for my daughter i'd defeat the demon king and a lot of other stories that are written by women have girls wanting to get saved and marry an older guy. Inuyasha is the last controversial one, and people says that yashahime isn't canon and stuff like that because Sesshoumaru has kids with Rin.
I think that if it's not of the intention of the guy exploiting the girl and not doing any sort of grooming behavior, and it's of the girl's own free will, then it's perfectly fine and not disgusting. Or I guess that the main difference of disgusting if it's the guy is exploiting the younger girl or not.
for real this is how I’d be in an isekai, even if I could figure out it’s related to a game I played wouldn’t remember enough to be like those clever/scheming MCs who can manipulate the story I’d just be fucking around