JUJUTSU KAISEN S01 E46 Metamorphosis (2)

"A boy fights... for "the right death.""

The moment it appeared Itadori and Mahito's battle to the death was resolved, the being wearing Geto's body asked, "Shall I save you, Mahito?" Itadori immediately recognizes the man before him as the very same one who sealed away Gojo and leaps to attack.