I like the aesthetics, the area we're in is pretty mysterious and fun to explore, a lot of nice details here and there, makes me wanna think what happened, why that happened, why are we here? And why does feeding your tamagochi refills your weapon?! I like aiming and rolling, enemies are... weird? Why skeletons use brooms? Why futuristic mecha ninja? Why big green glowing skeleton that looks intimidating but has no attacks?
Tamagochi part is pretty cute, but I'm wondering about the necessity of it. Obviously that's the main thing you want to incorporate into the game and reloading is simple enough but I had to go couple of times to wash the thing. He gets dirty very fast, I don't know why should I do it, it uses no resources and right now seems like a waste of time. If it's necessary and your gun can jam (for example) then washing shouldn't be a thing that happens every 3 minutes. I see you have additional options in it, like a map? I hope that your pet can grow and will add offensive power to your gun and extra options can help us in finding secrets or navigate the terrain. Also add a chance to make him sick! Imagine a scenario in which you can't shoot when your pet is sick and you're looking for a specific item that can cure him.
The scarcity is something that you'll have to balance, right now the vending machine spawns everything for free (I presume it's for testing) I think that enemies dropped something once or twice. You can eventually add items that are scattered around the gameworld and that would incentivize exploring.
I found a bug that removes level geometry when you're aiming and you have obstacle behind you.
Your game has a lot of charm, I really liked low-poly models, animations are very good, the flashlight is neat, works as intended and adds more mystery to this world, music and sound effects are also nice. I believe I reached the end of the demo with big green one and stairs that I couldn't climb up. You have a nice concept and a fleshed out start, I'd love to see more and where this is going!