I've had this game on my mind days after I first tried it.
At first, I didn't think much of it, but I came back realizing it made an impression. I think you've got something going with this. It's kind of cool that you have the anime character there reacting to the game. It's interesting and amps up the jump scares.
The scares in this game are very simple but effective. I was honestly surprised that they caught me off guard because I was expecting them to happen (slenderman-esque experience).
Once the novelty of the idea wears off, however, it does start to feel like the concept drags on. When you've been scared 2-3 times by the jump scare and had a sneaky spike death, you kind of "get it" and move on. But for a game jam sized game, I think you've found a fun concept worth exploring.
My suggestions are to do more with the anime avatar <-> game. Perhaps the monster starts to have an actual impact on the anime girl that's playing the game, and that effects the game. Like some sort of meta-game horror thing. A way to push back on the monster would also be nice. What really is lacking is variety in the experience because once you've died once or twice, the alure of the game starts wearing off.
Either way, a really nice project and I'm glad I gave it a chance. I hope you do more with the idea!