As rough prototypes go, this has a lot of potential. I'm a suck for novel story presentation for IF shaped things. I am unfortunately easily bored by box-of-text-in-the-same-place. However, these cards allow for a decent bit of text that never feels too long nor to short. I also don't think I've seen a Reign style game for an erotic game. I think this little engine could be the basis of a bunch of narratives.
One piece of feedback I have is maybe having a setup like:
That way the choices stay readable and don't have to fade-in and out. Aside from that, I hope you manage to put this engine of yours to work in future projects. Looks like it'd be fun to work with.