Demyx first appeared in Kingdom Hearts II at Hollow Bastion with the other Organization XIII members. As revealed in Kingdom Hearts II Final Mix+, Demyx was reluctantly assigned with looking over Sora’s progress in the Organization’s plan, complaining about it when he reveals himself to Sora when at the Underworld with possession of the Olympus Stone, an object that protects the bearer from the effects of the Underworld. After attempting to talk to Roxas through Sora, Demyx sends his water copies after him and leaves after losing. Demyx later crosses paths with the protagonists again at Hollow Bastion during the Heartless attack, constantly mocked because of his apparent incompetence and behavior. However, once Goofy brings up that as a Nobody, he has no heart, Demyx commands the “traitor” and his friends to be silent and gets serious in attacking Sora. Demyx fades into darkness at the conclusion of the battle.