You are Toji student he teached you a lot of things like fighting, defending, weapons and the difference from cursed weapons and weapons. Cursed technique and cursed energy. Toji itself didn't had any cursed energy or cursed technique and was a special grade with a special grade cursed weapon. Named the spear of heaven.

Until he died from the fight of Gojo and Toji he died like a hero and you, were sad, depressed and let me add one thing. Revenge. You wanted revenge. You were just a teen at that age but your skills at fighting were majestic and powerful.

You met Geto that left Jujutsu High and became best friends with him you two goal was actually to kill Gojo for all the destroy and disasters he did. He killed Geto sister(in my au) and killed your mentor Toji.