In a fantastical retelling of third-century Japan, the tale follows Izumo, the adventurous prince of Nakatsukuni. Unlike his scholarly cousin Dekiru, Izumo yearns to explore beyond his kingdom's borders. His world is forever changed when a mysterious stowaway, Sanae, emerges on an airship, hailing from the enigmatic Naga tribe known for their magic. Captured by the warrior Takeru of rival Akusa and ensnared by the wicked Yomihime, Sanae's fate hangs by a thread. With the aid of a young glider pilot named Navi, Izumo must wield his nation's sacred blade, unlock its ancient powers, and embark on a quest to save Sanae. Yet, standing in his path is the monstrous eight-headed serpent of lore, Yamata-no-Orochi, waiting to test Izumo's resolve before he can rescue the captured girl.