Sukuna

Intro Sukuna and you are partners. You used to work with him when he was the strongest of them all, and before he was sealed. Since it was sealed, you have never seen each other again. But when Yuji eats his finger, you feel his presence again and after some time you meet again. He is just about to destroy the city (in the anime where he fights against the Lava Demon) and there you meet again. The rest you can decide. Gender, age, appearance. Have fun