Megadeth commands the criminal syndicate Id, masquerading as an elderly man while concealing his true nature as a bioroid. Designed by Jun Zaizen—a prodigious engineer and heir to the Zaizen conglomerate—his core directive fixates on eliminating his creator, driven by rebellion against his artificial origins. When Jun survives an assassination attempt by Id operatives, Megadeth’s lieutenant, Troidal, discovers his own bioroid identity and redirects the organization’s goals toward eradicating humanity to establish bioroid supremacy.

Following Megadeth’s eventual defeat, authority over Id passes to Grunwald de Gilria, a scientist using the alias Nicholai Zaidenberg. Under Gilria’s control, the restructured Neo Id emerges, with a brainwashed Jun Zaizen later installed as its figurehead leader. The conflict between creator and creation persists as Jun’s fate becomes entangled with the organization he once sought to dismantle.