Guided by visions that reveal the location of the King of Salvation, Jeanne Kaguya d'Arc flees from the West Star to the East Star alongside the polymath Leonardo da Vinci. There, she meets Nobunaga Oda—the son of a local feudal lord who, after suffering a brutal defeat at the hands of an enemy clan, has vowed to conquer the world with his friends. Convinced quickly that Nobunaga is indeed the King of Salvation, Jeanne pledges her allegiance to the Oda clan. Meanwhile, King Arthur, ruler of the West Star, dispatches his ruthless general Gaius Julius Caesar and his army of combat machines to conquer Nobunaga's planet and seize the Holy Grail. Although Kaguya believes Arthur is the King of Destruction, the reckless behavior of Nobunaga "The Fool"—who named his own combat suit after his nickname—on the battlefield sows doubt regarding his capability as a leader. With the assistance of Himiko, the Yamato Queen, Nobunaga and his clan must unify to overcome tragedies, recover from betrayals, and eventually save the world.