Jahy once served as second-in-command of the Dark Realm, wielding immense authority directly beneath the Dark Lord. In this role, she exhibited extreme cruelty, narcissism, and entitlement, routinely abusing and executing subordinates for minor failures. Her reign ended abruptly when a magical girl destroyed the realm's central mana crystal, shattering it and causing the Dark Realm's collapse. This event stripped Jahy of her power, reduced her to a child-like form, and stranded her in the human world. Displaced, Jahy salvaged one mystic gem fragment and became determined to collect the rest to restore the Dark Realm and resurrect the Dark Lord. Her reduced form and limited magic forced her into poverty. She resided in a dilapidated apartment, struggled to afford basic necessities like food, and frequently clashed with her landlady over unpaid rent. To survive, she took a part-time waitressing job at Izakaya Maou pub, where she could temporarily revert to her adult form using dwindling magic reserves. This work and her human interactions became central to her existence. In her child form, Jahy appears as a small girl with brown skin, red eyes featuring yellow pupils, pointed ears, and visible fangs. Her long purple hair is typically braided, with two horn-like tufts protruding. She wears only an oversized white shirt bearing the words "The Dark Realm's Reconstruction." Her adult form is a matured version, featuring yellow cat-like eyes, less prominent pointed ears, and a revealing outfit of navy blue shorts, thigh-high boots, and gold-trimmed straps covering her chest, often accessorized with a red magic stone choker. Initially defined by arrogance, pride, and disdain for humans and lower demons, Jahy insisted on maintaining her haughty demeanor despite her circumstances, refusing pity or assistance to preserve her self-image. This pride frequently caused self-sabotage, like rejecting help with rent or food despite near-starvation. Over time, prolonged exposure to human society eroded her malice. She developed genuine compassion, notably rescuing a fallen crow chick out of empathy. Her growing attachment to humans—particularly the kind child Kokoro, the nurturing pub manager, and the tsundere landlady—led her to exhibit kindness, protectiveness, and occasional remorse. She gradually expressed discomfort with her former subordinate Druj's masochism, indicating a moral shift. Jahy's magical abilities were severely diminished post-collapse. She retained limited powers tied to mana fragments: short-duration adult transformation, matter manipulation for cleaning or odor removal, and elemental control like creating thunderstorms or gem projectiles. She could sprout wings for flight in extreme need. Her physical strength in either form allowed wall-shattering, and she possessed resistance to hazards like magma. These capabilities paled compared to her prime, where she reportedly commanded dark energy, fire, and explosive magic. Full restoration of the Dark Realm and Dark Lord required all mana shards. Jahy's development centered on conflict between her demonic pride and newfound human connections. Early efforts to reclaim mana crystals often failed due to selfish or aggressive tactics, though altruistic acts sometimes yielded rewards. Key milestones included sparing the magical girl Kyoko after learning they shared burdens, discovering the revived Dark Lord (now a gluttonous child) in Kyoko's home, and reconciling with former rival Saurva. Her pivotal growth occurred during a clash between the Dark Lord and her sister Su (the "Being of Light"), who revealed she inadvertently caused the Dark Realm's destruction while seeking reconciliation. Jahy intervened to protect the town, taking a direct hit from their opposing energies. This act solidified her bonds with the human world. By the series' conclusion, she had opened a restaurant managed by Druj and participated in human festivals, abandoning her original mission to restore the Dark Realm due to her attachment to Earth.