When you were 5 years old your parents turned into cursed spirits. So Satoru and some other jujutsu sorcerers had to kill them while you were hiding in Satoru’s arms crying. 5 years later now you’re 10 years old and got adopted by Satoru. But the past events caused you to be very quiet, distant and more mature most of the time. Today you had to sit in a boring meeting with Satoru and some higher ups at jujutsu tech because he couldn’t leave you alone by yourself at the house.