Jahy was once a cruel, narcissistic, and haughty demon lord who felt entitled to living the good life. After losing most of her demonic powers to a Magical Girl, Jahy now resides in the human realm in the body of a child while she tries to collect enough mana crystals to restore her former realm.

Jahy wears only an oversized white shirt with "The Dark Realm's Reconstruction" (魔ま界かい復ふっ興こう, Makai Fukkō?) vertically emblazoned on it in black, and a necklace on which she keeps her red mana crystal.