The era is the Warring States period, and the battle between the Gundam Army and the Dark Army continues. Each side controls roughly half of the entire territory, leaving only the Momi-no-Ki Plains. It is said that whichever army raises its own Shachi-hoko atop the keep of the phantom castle, Abaowakuu Castle—which appears only once every 333 years in the Momi-no-Ki Plains—will conquer the land. Before the appearance of Abaowakuu Castle, the war begins. Gazuaru and Gazueru seize the Shachi-hoko of the Gundam Army. Hyakushiki and Hyakkimaru attempt to reclaim it. Furthermore, Saiko of the Gundam Army, wearing a brainwashing mask, becomes a member of the Dark Army and attacks his former comrades. Amidst this fierce battle, Abaowakuu Castle finally appears! Screened together with "Mobile Suit SD Gundam's Counterattack: The School Festival That Summons the Storm" and "Patlabor: The Mobile Police."