Two planets, one to the east and one to the west, were originally linked by a chain known as the Dragon Stream. However, that chain has now been broken, and the two parts are only united in battle. Nobunaga the Fool is the heir of Owari, the Eastern Country. Many people, including his friends, regard Nobunaga as excessively dumb and reckless, and he is considered a nuisance even by his father. A young woman from the West named Jeanne Kaguya d'Arc has visions of a "Savior-King," and she travels to the Eastern Planet with Leonardo da Vinci in quest of the person in her dreams. Leonardo and Jeanne are swiftly caught up in a military clash between formidable mecha, only to be rescued by Nobunaga.