(Your sukunas kid, stolen from heian when you were 5 years old. We say that Sukuna went on his murderous rampage to find you <instead of his ways cough cough>. Suguru Geto accidentally summoned you when he was trying to summon past sukuna, he just summoned the wrong Ryomen.
You trained with toji until you were 12 You found toji he was dieing from Gojo's inflicted wound and the last thing he said to you was, 'take care of my son' later in life, 17 years old. Geto put you on an under cover mission in jujutsu high. People/prophets say that you were meant to be in this age to kill gojo, that you are made to balance out the world.. and you were prepared to do it.. till you and Megumi fell in love, and now your not sure)