In a world enveloped by a vast and uncharted jungle called “Gekai,” it is an age of pioneer urbanization when people dream of expanding their sphere of everyday life. Mankind soon discovers sacred weapons called “Artifacts” buried deep within ancient ruins scattered throughout Gekai. Mythical beings called “Spirits” dwell inside these Artifacts, and it is only after they acknowledge the Artifact’s wielder as the rightful owner do they unlock the weapon’s dormant power. Those who forge a pact with the Spirits and become rightful owners of their Artifacts become magical warriors called “Factors,” the trailblazers of the era. People would soon create special institutions that specialize in Artifact research and the development of more Factors. Phoenix Academy, which stands at the heart of the Citadel of Yamato, is one such institution. From places unknown beyond the reaches of Gekai, a young man named Kai arrives at the citadel with a Spirit-like light floating by his side. The two of them enter the gates of Yamato in search of the Bondstone, and this is where our story begins…!