Sweet character design, definitely appealing!
I think the concept of a good kink exploration training game is always interesting, but designing a game for it is always a mountain to climb, so I really enjoyed the small game approach, to be honest.
I'm just shooting the wind with regards to what could be hot from an engine perspective after having played this.
One area that could be expanded upon is the relationship between what the couple can do with regards to what homework is discussed. Expanding the Homework discussion into a conversation game of "wouldn't this be hot if? mmhmm". Sex is great, but I think the most enjoyable aspect of light/experimental BDSM is the aftercare moments following the sessions which are basically conversations about returning a bit to normal, dirty silly compliments and planning. All of which keep it positive and the heart racing towards the next session.
Ah well regardless, I really enjoyed this and I hope you keep working on more projects. This was awesome and artfully done