In the past, an orb-like heart created by the pure soul of vows managed to imprison seven demons that threatened the seventh moon. However, the creator of the orb was devastated during the century's judgement, which also affected the orb, causing the monsters within to awaken and seek their ideal physical state. As humans are transformed into their demonic selves, Seikashi takes control of Ikatsu to end their unfinished mission and bring an end to the darkness beyond eternity. The story follows Ikatsu, a young boy who dreams of being a stage actor but begins to despise each day that passes. As his emotions become filled with rage and vengeance, he becomes the ideal host for Seikashi, but ultimately, he finds a new sense of hope for the future.