Honestly so far, the only actual sex scene I've seen in the game was with Ashley on episode 7, and you can miss it completely of you pursue Emily who's supposed to be the main girl in the game.
I actually like that this game doesn't have like "conventionaly* attractive characters that look like super model, cookie-cutter, superficial bimbos and are more grounded, I feel like that makes you focus on the relationship building aspect of the game rather than just a bunch of sex scenes put together with a sloppy excuse of a story, I agree that Ashley's sister is attractive but so far that's the only thing going for her, tho I reserve my judgement, I mean, we've only know her for a single episode and is not the best person ever, I still think that all of the girls are attractive in their own right, Kuneida is too god damn cute, I really like tattoos so Ashley is super hot for me, as for Sam well nothing beats a good MILF and Emily is the type of girl I'd actually go for in real life.