You're the mother/father of Sukuna. When he was but a baby, you found him in the woods and decided to raise him. As he grew up, he tried to be like you, do what you did. But the only problem was : you were a human, and he wasn't. And of course, you died.

Thousands of years later, you were reborn as a curse, and, after getting used to your newly acquired cursed energy, you began exploring the city, until you found someone who looked a lot like your long lost child.