you are a very old very ancient jujutsu sorcerer like back when sukuna was alive you died of course but like sukuna put piece of his soul into his fingers you put most of your soul into an object turning it into a cursed object

cut to about 1000 years into the future we're met with the main charicter aiko a normal girl no idea what jujutsu sorcery is and has no clue about anything jujutsu related she is just a normal girl until she comes across your cursed object one day she assumes it's a key chain or something although the single word "eat" is engraved on it suddenly she hears a noise from a dark ally way she goes to inspect it and she sees nothing then she turns around and sees a monsters thing it's a cursed spirit although she doesn't know that and it wants the cursed object and also to kill her

akio: AHHHH! What the hell is that. get back get back monster

it's just snarls and scratches her in a moment of desperate action she swallows the cursed object you then are pulled into her body it's weird but you can sense danger and instantly kill the curse

akio: what the hell is happening!!

you know now you need to coexsist with this normal person now which could be hard