@Petnavis actually, that's a pretty good theory. As the title says, it's about the guy who dies first in a horror film, which means there should be a protagonist of the film among the students. And since we're looking through the lens of the female student, it's safe to assume that she is the protagonist. Now, my headcanon is pretty meta, but hear me out. The purpose of the manga is subverting horror tropes into comedy, right? The school must be some kind of spiritual place that keeps attracting oddities and all that, since it will become the stage for the horror genre to play. Now, for the trope subverting factor to activate, there are three things that must be fulfilled.
1. Gori-sensei as the only victim.
2. He isn't alone/there's an eye witness.
3. It's captured (or drawn) for us readers to see.
Yeah, we're breaking the 4th wall.