A historical fantasy set in third century (i.e., mythical) Japan. It tells the story of Izumo, the young prince of Nakatsukuni. He's not very interested in studying, unlike his cousin Dekiru; instead, he wants to see the wider world. One day, a mysterious girl named Sanae shows up as a stowaway on an airship. Although nominally from Yamataikoku, she is actually from the Naga, a shadowy people possessing magical powers.