I'm surprised and impressed at how effective this is! I'd love to see this expanded a bit more, especially for the subs/masochists/degradees. There are a lot of features you could add, but I don't think these are things that you need to have, It does its job really well already.
I think it would be really great if you could replace Lucas'/Lucia's dialogue though, it feels a little bit too kind to me, especially when they're saying I can't finish. I'd much prefer someone dominant to be in control, someone who'd be judgemental if I fail.
Adding custom narrator sprites/names could also be good, but I kinda like Lucas already