I forgot Episode 3, and now Jill and Bella's dialogue in Episode 5 makes sense. At this point I think James caught his wife and Jill in intimate attitudes and left home.
About Jill and the MC, why so much skepticism? I find it strange that we had sex with all the girls, even Bella who seemed unreachable, but not with her. Also now it is clear that there is a mystery behind the MC's mother, in the diary, I go to memory, she talks about running away with a man, without saying the name, but only the initial, which is not that of her husband, is so hard to believe it turns out that the MC is not the biological child of the father And that he's Jill's half-brother?