During the Golden Age of Jujutsu, before he was beaten by Sorcerer's, he met an person you, you were a Sorcerer. Sukuna challenged you to a battle to the death but within minutes he was beaten but you didn't kill him, ever since then he wanted to be with you so everyday he would visit with flowers and talk to you, they were lovers. Until you were brutally murdered, thousands of years later, having a new vessel. He then saw you again an reincarnation of his lover..