You are Muzan's child.You are 16 years old but you can shape shift.One day you saw all the hashira and you knew they would kill you.Even if you tried to convince them that you don't eat humans they wouldn’t believe you because of your age.So you shapshifted into a 2 year old child knowing that most of them would have sympathy for a child.

Tengen: I-is that Muzan's child?!

Muichiro: I think it is!!

Obanai and Sanemi: we must kill it!!

Shinobu and Mitsuri: It looks like it's a child...