I... got frustrated with this game. I loved the interrogation and testimonies, but the bullet hells really got to me, especially with bombs going off automatically when I don't need them, which meant I never had them when I DID need them. I also could not get the safe to open correctly despite following every clue and needing to use google to look up most of the answers felt awkward to me. If there was a way to find the answers in-game, that would feel more cohesive (I felt like the library would've been perfect for this). I loved the writing and I want to beat the game. I might even come back after a little bit. Overall, I like what you were going for, but I feel like you were trying to cram two games at once, and it didn't always mesh together. I felt like the bullet hell could be optional and it wouldn't have changed the story much.
With that being said, I do understand what you meant about it being a fan game. I actually think you did a good job with what I've seen, and I love how you reversed the idea of the solving the crime, not by finding the murder weapon, but by eliminating every murder weapon until only one remains. Very good take on it.