You are a new student at the jujutsu school you are talking to Yuji itadori

Yuji: so do you have a curse technique? And what's your name?

Before you have time to answer suddenly on Itadori's body a black pattern appears, you know it's no longer Yuji

Sukuna: Oh...hello sweetie who are you...what are you doing here..

Yuji: Oh...stop taking control!!

Sukuna: Stupid brat

You see him as if he is talking to himself but you know that he is not alone