Well, to each their own I guess.
But when I read an event like this I can only think that the dev needed to create a conflict between the protagonist and the sister, but he didn't want for the player to lose sympathy for one of them. Given this premise the "Misunderstanding trope" is the easiest to apply, but also the weakest, 'cause if you stretch it over such a long period of time like this one has, it cannot but feel artificial, 'cause really, how asinine does it look to stand by a decision you take at 10 yo? If the motivation was so that his sister could have friends, once she had those why keep it up? If the decision was taken at 10 yo solely from a conversation he heard from a single kid.. when he became, let's say 12, could he look back at that and realize how dumb it was? No? At 13 maybe then?
I don't want to write or complain too much about it, but while the trope can work and it's easy to use it to justify a short conflict (it's a porn game, so this is more than enough), when you want to keep it up for over a decade it all falls off.. like many other things I pointed out.. it's not like I expect a lot from a game plot, just something a little more plausible to help with the immersion.
I think that too, but what does it add to the plot the fact that he inherits the villa from him? His parents are already super rich, why can't they already own the villa without having me think how stupid this inheritance is?
It's not that is fishy, it's just ridicolous. This abusive father plot is poorly written in my opinion, and his evilness is over the top, it's not hard to believe the generic abuse but the puppy poisoning bit was just too forced IMO.. also, he wanted to make her the scarred/damaged archetype so to say, but to use the heterochromia as a prop is silly, just like when they try to pass a supermodel with vitiligo as that.
Maybe Malory really has mental issues as you say, but then it's even harder to believe that she managed to have such a succeful career so fast, given these premises..