Do you think that in a future build, like let's say build 65 or build 70 or whatever, you could give the player an option to make the shadow NPCs a little aggressive? For example if they see the player masturbating they will approach the player character and start fucking them themselves? If one wants to join it will start a duo, if another gets interested they might start a threesome, or even more may join.
It can be a toggle feature. I ask this especially since it seems you intend to make the shadow NPCs cuter.