Mercedes, a red-haired succubus, works as a demon harvesting human souls for conversion into underworld crystals. She collaborates—and clashes—with Carrera and Rati, her rival partners, bound by a shared mission and volatile dynamic. Her relationship with Carrera veers between camaraderie, romantic friction, and cutthroat competition, fueled by envy over Carrera’s higher soul-collection success.

Though fiercely dedicated, Mercedes’ overzealous work ethic backfires comically: she stumbles while transporting meals, wrecks plumbing during tasks, and often retreats to the underworld defeated, her hands empty. Her fixation on outperforming Carrera eclipses practicality, undermining her efficiency.

When summoned by Ogawa, a vengeance-driven human entangled with demons, Mercedes seizes the chance during Carrera’s imprisonment. Ogawa’s clear preference for Carrera, however, provokes her resentment. Their confrontation spirals into a public sexual encounter forced upon her, deepening her humiliation and sharpening her rivalry.

Unlike Carrera’s bold confidence, Mercedes flushes with embarrassment during intimate moments and professional failures. She boasts diverse skills—from scrubbing bathrooms to plotting global domination—but her execution wavers, mixing occasional competence with haphazard results.

Amid a celestial invasion targeting demonic soul-harvesters, Mercedes grudgingly allies with Ogawa and others to free Carrera and Rati from angelic captivity. She fights in the decisive clash against heavenly forces, showcasing loyalty to her partners despite their rivalry, though Carrera remains the conflict’s pivotal figure.

Her history before demonic service remains undisclosed, her actions and relationships anchored to her duties, rivalry, and the fallout of her impetuous choices.