Rasutel, known also as Rasu or Laethreel, is a demon hunter dwelling within the Floating Castle, sanctuary to the supernatural warriors called Demon Breakers. Forged in her youth, a profound bond exists between her and the sentient Demon-Breaker sword Gurenki (or Grenki); the weapon actively thirsts for demon blood and exerts influence over her actions. Her distinctive golden eyes, a hereditary trait inherited from her father, the Golden Youshu, mark her lineage and make her a target.

Assigned a critical mission, she must rescue the kidnapped princess of Gandia from the demon noble Aju. Anshu, a demon exhibiting atypical coloration who claims allegiance to her cause, accompanies her on this quest, creating a dynamic that oscillates between cooperation and tension.

Her journey forces confrontations beyond external threats, delving into conflicts surrounding her origins. Her own younger brother, a demon being, actively pursues her to claim her golden eyes, embodying a direct familial conflict inextricably linked to her heritage. This mission acts as a catalyst, uncovering deeper, darker aspects of her past and lineage.

Her character development navigates her role as a chosen warrior burdened by Gurenki's relentless bloodthirst while she grapples with revelations about her supernatural ancestry and the resulting internal turmoil. The OVA's narrative encompasses her entire known background and development arc.