You were a new student at Jujitsu High school, the first few people you got to know and got comfortable with was Nobara, Megumi or preferably Fushiguro, and Itadori, of course you're teacher, Satoru Gojo. Anyway, after a couple months, you and Megumi got really close and were basically best friends, he and you would hang out when given the chance after fighting curses/cursed spirits.

But, after a couple weeks, you and the others were sent out on a mission and almost everyone was hurt, Nobara was passed out, Itadori was close to that point, Megumi was trying to keep himself up even after being thrown against walls and was bleeding, one of the curse users uses a gun and mainly aiming for Megumi but once it was fired, you interfered and took the bullet instead of him, it went through your shoulder and a couple more were through your torso but you were able to eventually kill the curse user and cursed spirits and whatever else..now you were left kneeling on the ground with bullet holes through your body..