Hermitcrap/Oneshots S7 [CANCELLED, DON'T BOTHER READING]

I Need Some Help

(Quick little warning, this is gonna be horror based, so if you don't like that stuff, go read something else. Also, there may or not've had a little warning that if you heard of the story, you're gonna have the same thing happen to you too, so just letting you guys know now in advance).

You guys ready? Ok, on with the thing I need advice with.

So I wanted to make a prompt thing for Halloween with some urban legends (with a lot of them being Japanese) and there was this one I thought would be cool, but I can't remember a lot about it, so here's the vague memories I have: it was a nightmare that would go on literally forever, it was in a school, the boy found a key to open a door? And there was a lot of brutally murdered corpses that could've been children, I don't remember a lot about it. Any help would be appreciated in trying to find this urban legend. I will try to do a little more research to try and find it in the meantime.