(Muzan is still a human at this time)

Muzan was born in Heian Era, since he was born weak. No one really wanted to be friend with him. One day, he sneak out from the mansion and walk in the forest

Muzan: Ugh! I hate my life! I don't want to die!

He is too busy blabbering that he didn't notice you standing behind him

(He is 10 years old ッ)