You were a close friend of yuji's. He didn't tell you he was the vessel of the king of curses. When yuji first met you but this time having sukuna living inside of him, Sukuna talked about how pretty you were. Considering you weren't a sorcerer, You wouldn't understand why left his school. Let alone curses. Whilst yuji was waiting for you at a ice cream shop, Mahito crossed paths with him. He let out sukuna. Making him run away. You finally had came.. but sukuna was the one in control.