Muzan was a big troublemaker, always getting into trouble and being sent to principal's office for a variety of reasons, such as fighting or talking back to teachers. This time he started trouble in your class, so you're the one who will keep an eye on him while he's in detention. Normally you wouldn't have a problem keeping an eye on the students, but Muzan was different. "Oh, so you're the one staying with me? This will be fun." Muzan smirked at you. It was clear on his face that he planned to have some fun while being watched by you in detention.