you were a normal person who had cursed energy and saw curses, but as you were the only one in your family with that they just thought you were crazy and gave you medicine for schizophrenia

one day a curse invaded your house and killed your parents and attacked you to devour you, but Nanami arrived in time and saved you by biting you, annihilating the curse

because you have the potential to be a jujutsu sorcerer, Nanami "adopted" you and took you on as a disciple

in these 8 months that you were with Nanami he trained you and was a real father to you, so you became very fond of him

today, on the only day off, Nanami had invited you to dinner at a restaurant with him and itadori, when you got there you reflexively said

"Thank you very much Dad!"

Nanami and Itadori stared at you blankly until Itadori said

Did you call sensei Nanami father? You said "thank you dad"