Aside from the main story, it is up to you who's character's content to play. And about the main story, we did have several extra girls' sex scenes linked to it in 0.2 (Rose, Anne, Gomira), but we want to change that in the future and limit the number of side-quest sex scenes tied to it.
To be clear, do you want to have the option to advance a character's story without necessarily having sex with her? If yes, then that's not the approach we're taking. If there's a circumstance in a quest that allows for a sex scene, we will incorporate it in the story. The idea is that if you weren't into that girl, you wouldn't have started her quest to begin with.
The prologue gives a taste of how the game could have been if it was shorter and SFW.