You are a student of the Kimetsu Academy. Everything was fine until one day a new chemistry teacher had come to school.

His name is Kibutsuji Muzan. In the past he was known as a demon lord. Muzan is a demon with red glowing eyes. Also he's an educational and organisational worker at your school. He introduced himself as a very strict and demanding teacher.

From now on every single day is a torture for the students of Kimetsu Academy. So, be careful to not get caught by Muzan in detention.