In regards to the other game on your list, in short the MC is once again a horny, 18 y.o., just back from school for the summer when he starts to perv out on his mom, which if you've seen her, is perfectly reasonable. What isn't is, the depths to which he will go all cringey and rapey to get into her pants. It's a slow burn that despite having a setup for a harem, the MC becomes obsessed like a stalker (even with other females around to focus on) stopping at nothing, including sexual assault (sleep sex mostly) to get action with her. He does succeed in slowly corrupting and seducing her so she is at least consenting, but even when she tells him NO, he still forces himself on her because "he can't help it and is too horny". So far in the game they've gotten at least to oral sex foreplay and some grinding but no P-in-V yet. It's ridiculous because literally everyone else in the game is having sex including his lesbian/bisexual sister and a cheating, nympho-aunt who literally fucks every other guy, but somehow has friend-zoned him, along with the other milfs in the game... oh and its more or less a kintetic novel with the only choices happening early in the game and leading to a 'game over' if you pick the wrong one.
Getting back to Summer with Mia 2, you actually have the option/choice to decide if the MC will cheat on his now current girlfriend, but no harem options just yet. The aunt does have quite the promiscuous past which she will share with the MC in flashback scenes only if you want to see them. Believe it or not, the MC in the sequel is dreading reuniting with Mia since they did not leave on the best of terms, but all he is interested in is repairing his relationship (as just a brother) to Mia while staying loyal to his girlfriend. So through the first 4 episodes/chapters, there is a decent amount of character and plot development and for once, the MC isn't a piece of shit (unless you want him to be)....
While the girlfriend is cute and loyal, I still was really pulling for my MC to get back together with Mia as they both show they aren't exactly over each other yet. It's predictably awkward as Mia now has a boyfriend while the MC has a girlfriend of his own. For me, I'd rather just break up with the girlfriend since she doesn't deserve to be cheated on and I'm not exactly getting harem/sharing vibes from her.