身为贵族的儿子却埋头于研究魔术和炼金术的少年蒙莫朗西，
在巴黎的王立骑士养成学校，身边聚集着布列塔尼公爵的妹妹里什蒙
等众多的骑士、姬骑士候补，过着慌乱而又充实的每一天。
但，随着阿赞库尔之战的大败，法国与他们的命运彻底改变。
巴黎陷落，骑士养成学校也被关闭，
失去了一切、成为在逃流亡炼金术师的蒙莫朗西，
在逃亡前往的村子里与不可思议的少女贞德相遇了……。

The story is set in the 15th century, during the Hundred Years' War between France and England over the succession to the French throne. Montmorency, the son of a noble, immerses himself in the studies of magic and alchemy at a royal knight training school. However, following France's crushing defeat at Agincourt, the school is dissolved. Having lost everything and now a wanted man, Montmorency, who had just become an alchemist, encounters a mysterious village girl named Jehanne.