Sosai Z is the regenerated form of the alien Sosai X, emerging after X's destruction at the end of Gatchaman II. A surviving fragment of X's body rebuilt itself, evolving into a more menacing mechanical entity driven by intensified vengeance. Z functions as a colossal mechanical factory with advanced capabilities to design and produce iron beast mechas. It deploys these creations in destructive campaigns against Earth. This form embodies X's lingering consciousness but exhibits heightened ruthlessness and strategic aggression. Z's core motivation remains the complete annihilation of Earth and humanity, fueled by spite upon learning of his home planet Selector's destruction in the Andromeda Nebula. To rebuild Galactor's forces, Z recruits the human dictator Count Egobossler, offering technological supremacy in exchange for loyalty and military expansion. Their fragile partnership sees Galactor launch widespread attacks using Z's mechas, occupying territories and eliminating dissent to consolidate power. Z's central scheme is Operation Poison Apple, designed to redirect an antimatter asteroid into Earth, causing global devastation. This plan culminates in a final battle within Z's pyramidal fortress. There, Z deems Egobossler expendable and eliminates him, assuming direct command. The Science Ninja Team's intervention triggers an explosive chain reaction within the pyramid, ultimately consuming it in a black hole. Amid the collapse, a phoenix-like entity is observed escaping; Z itself is not shown surviving the event.