Pretty good game with a lot of potential. There are a few things you could add in my opinion:
1.More belly interactions without minimizing. For example, you could add an interaction function switch that allows you to pet the demon's belly or squeeze it in your hands (I also think it would be nice to add a button that allows you to interact with the demon's belly without minimizing the belly).
2.A change to a female version of the demon? (I love girls, even though he's cute on his own it would be nice).
3.The ability to pet his thighs or butt), I don't think anyone would mind.
Again, these are just suggestions and you are not obligated to do them, but it would be just fine. So good luck with the project and take your time. All the best to you.
P.S. I speak a different language, so there may be mistakes and weirdness in the text.