This has the potential to be really great, the girl is absolutely gorgeous and I love the idea of 'taming' a yandere. It would be amazing if instead of just being her lover or her plaything, one could also be her dom, like when she can't help herself from breaking the rules he sets down, he disciplines her and brings her crazy side under control that way. She does keep on saying she'll do anything, after all.
The downsides though; it's a poor design decision IMO to lock scenes behind not doing anything with her, it would be better if those triggered randomly (progressive random, to ensure they do trigger) and then gave the player a choice how to react that would determine how they would influence her development.
Also, him perpetually insisting that they can't do anything is pretty weak, it barely makes sense on the love route, it doesn't make any at all if you're not trying to rein in her crazy side. And I say barely because even wanting to take it slowly, he's taking it ridiculously slowly. The 'gameplay' portion is without a doubt the weakest part of the game, the VN portion before it is much better.