Fortune favors Inuyasha and his companions when they finally vanquish their foe Naraku, who had inflicted relentless suffering upon them. Ecstatic about the hard‑earned triumph, everyone rushes back to their previous existence, oblivious to lurking peril. Kanna and Kagura, two of Naraku's lieutenants, plot to unleash a sealed demon that proclaims itself as Kaguya, the fabled Celestial Princess.
While absorbed in their separate quests, the band of Inuyasha reunites through a series of strange coincidences involving Kanna and Kagura, coupled with an uncanny recurrence of full‑moon nights. Realizing that Kaguya orchestrates the disturbances and wields a dreadful might, they unite once again to thwart the catastrophic destiny she intends for the world. Their resolve hardens, and they prepare to confront the looming darkness together in the night.