Erika Hiura is a high school student who casts curses, possessing short brown hair and distinctive pink eyes while typically dressed in dark, formal office attire. Initially an antagonist, she serves as a mercenary necromancer under her father's direction, her curse work linking her directly to supernatural incidents investigated by the protagonists. This role makes her central to escalating paranormal cases.

Depicted as enigmatic and initially feared, Erika's actions stem from paternal coercion rather than personal malice. Her trajectory shifts dramatically when the protagonists save her during a confrontation. This event causes her to shift allegiance, moving from antagonist to actively assisting in dismantling the network of curses and impurities maintained by her father's cult organization.

Her potent abilities include granting Kazuomi Sakaki a "deathless" bodily constitution after saving his life from a supernatural attack, causing the power to pass harmlessly through him. This transformation highlights her unique capabilities.

Erika's relationships evolve significantly. Initially perceived as a mysterious threat by characters like Kosuke Mikado and Rihito Hiyakawa, she later collaborates with them. Her background reveals a lack of agency, manipulated into being a curse worker. Once freed from this influence, she actively contributes to resolving the central conflict, transitioning from a weaponized individual to a willing participant in stopping the cult's operations.