ALL OF US ARE DEAD

Life at Hyosan High School is nothing special… until the students realize they’re in ground zero of a deadly virus that turns its victims into flesh-eating monsters. As the virus tears through their schoolmates in a matter of hours, they realize they have nowhere to run. Trapped in their high school with zombified versions of their friends and teachers, they must find a way to fight -- and escape with their lives. (Source: WEBTOON) — Description from AniList community (anilist.co).