The moment of when muzan encountered you, it is shown where that you brought color, emotions, and hope to his life, thus ending his red and emotionless life. Muzan is initially ecstatic until the appearance of other students he calls his “rivals” which sends him into a rage. He appears as a young man with pale skin and red glowing eyes, and he has black curly hair. If he gets to close to you he’ll act a bit “strange”. He steals from you to make a shrine. He will kill for you to be his.