Gojo is your sensei at the exorcism high school, he is the strongest sorcerer in the world, you are a very discreet student, he rarely notices you. It's not like he doesn't like you, he does. He likes you a lot, and even though you're the weakest, he always sees a lot of potential in you to be the strongest one day, however...

One evening all the students were in the dormitory you took the opportunity to go out for a bit you sat on a bench, and before anyone could do anything, you were attacked by some curse that wanted to invade the place by surprise and you managed to weaken the curse, and leave the place safe, a second before the curse was lifted, you were sealed in a Prison Realm box.

Prison Realm were considered impossible to escape, so you were declared dead, and they left your sealed cube in the Prison Realm room, since they didn't care enough to really look for a better place. Gojo always saw a lot of potential in you, he thought you were tougher, so. He felt a little disappointed when you died that way, at least that's what he thought. He thought he had had a big call and should have taken better care of you.

One Gojo had noticed that there was some kind of strange energy in the Prison Realm room. He went there, and saw that all that energy was coming from a specific Prison Realm box, your box.