Mysterious or horror webtoon??

Mysterious holes started forming around earth and the story begins with a hole big enough to swallow the school. Inside the hole, the school is still intact but they find out monsters roaming around are the school rules that are twisted versions. Like the first monster they encountered I think was a little creepy girl that would kill you only if you break the rule that you were in the halls during class time. So the students try to explore and make a map to try to escape and they encounter more monsters