That was cool! I can't imagine what kind of immense trickery you must have pulled to put VRoid models into MV3D like that. The self-aware humor like with the hover shoes was a nice touch but tbh I think it's amazing that this was done in such a short time, especially considering there's probably no easy way to preview what it looks like in the editor so you probably had to do a lot of testing. The image of the inside of that one classroom was dope and I can see from your profile you made it yourself as well!
I think I really like the potential of the game's concept the most. A Persona style anime game where a ghost girl helps you solve mysteries in the school sounds like I would enjoy it very much, I think you already established a core game loop with the first guy you're helping, and the concept of investing the spirit spheres to get stronger is very intriguing as well. To be honest I didn't quite understand exactly how I helped the first person, the ghost girl just told me I did it, but maybe I missed something or it's just not implemented yet.
It looks like you handmade not just the VRoid models and the levels but also some elements of the UI which is a lot of effort. The poses in the thumbnail are also really cool. I think if I would give one recommendation is to look into how to avoid visual noise in environments and UI (something I struggle with myself as well).