Jeanne is a girl raised in the country of Donremi on the Western Planet. She has heavenly visions of the birth of a "Star Messiah" who will save the world which leads her to go on a journey to the Eastern Planet with Leonardo da Vinci, "the one who observes the world." On the other planet, they come across the heretic of the Eastern Planet and "the greatest fool of the day," Oda Nobunaga. Oda had her disguise as a man and gave her the name Ranmaru to protect her from their kingdom's custom where women are treated as secondary class.

(Source: Nobunaga the Fool Wikia)