A blond fighting musician, Demyx (Demikkusu), the "Melodious Nocturne", uses a sitar as his weapon and controls the Dancer Nobodies. He does not enjoy fighting, but can control water with his sitar to replicate himself and to execute powerful and intimidating attacks. Demyx seems not to take his mission seriously at first, joking around with Sora and complaining that the higher-ups had mistakenly chosen him to carry them out, as he claims he is a poor fighter. He also confuses Sora with Roxas, having given orders by his Superiors to eliminate the "traitor."
Demyx first appears in the Underworld, where he is confronted by Sora for stealing the Olympus Stone, an object that protects the wearer from the restrictive effects of the Underworld. He fought Sora with the use of his clones, not taking the young Keyblade master seriously at the time and left after losing. The two soon crossed paths again at Hollow Bastion during the massive Heartless attack. Upon being reminded that he was a Nobody, and therefore had no heart, thus little, if any, actual emotion, Demyx fought Sora fiercely with his full potential. Unfortunately for Demyx, it was his last performance.