Read manga: Sleeping Dead

manga
Summary:

Earnest and well put together, Sada is a teacher that's popular among both his colleagues and students alike. One day after school, while he was on patrol, he saw a suspicious figure attacking a female student with a knife. Unable to escape in time, Sada ended up losing his life. However, Sada woke up on a cold slab... (Previously serialized with the title 'Living Dead')+