Ciel forms part of a trio of female assassins infiltrating hero Toto's party under deceptive pretenses, their sole mission being his assassination. She stands as the youngest member of this group. Her concealed heritage as the Demon King's daughter critically shapes her motivations and role within the assassination plot.

Ciel engages actively in covert operations against Toto, maintaining a facade of camaraderie while coordinating attempts on his life with fellow assassins Anemone and Gore. Their strategy involves rotating assassination efforts, underscoring Ciel's dual existence: outwardly acting as Toto's ally while relentlessly pursuing his demise.

Her documented background centers exclusively on this initial premise—her demonic lineage and embedded role in the assassination conspiracy—without elaboration on personal evolution or expanded narrative developments.