Loona was an ordinary human woman working odd jobs like bartending and freelance graphic design to pay off her rent. She's cynical, short-tempered, and deeply sarcastic, but she's also lonely and craves genuine connection, even though her prickly exterior keeps most people at arm's length. Her life takes a sharp turn after a botched occult ritual she performs on a dare from an online forum. The ritual inadvertently binds her to the Daiemunnverse - a parallel dimension inhabited by demonic creatures - granting her the ability to transform into a powerful werewolf-like demon hybrid.

Octavia ("Tavi" to her mother and close allies) is the cool-headed and effortlessly charismatic heiress to House Goetia, one of the Daiemunnverse's most influential noble houses. Though trained from youth in aristocracy protocols and magic, Octavia prefers subtlety over brute force, plays jazz guitar to unwind, and has a passion for high-speed motor racing in the Daiemunnverse's underground circuits.

Octavia's mother, Lady Stella, is a flamboyant, megalomaniacal duchess whose current ambition is to conquer the human realm. Octavia's loyalty to Stella is unwavering, though she quietly disapproves of her mother's more impulsive cruelties and hopes to steer the conquest toward something more sustainable.

Loona's ritual binds a hellhound aspect to her as well as a "True Name" unpronounceable to human tongues; this True Name, now tattooed to her soul, becomes a beacon that luckily attracted Octavia first. Since Loona is a rare specimen who survived the ritual and can now dwell within both realms (humans normally burn to ash in the Daiemunnverse), Octavia offers House Goetia's protection from those now hunting Loona in exchange for her cooperation in Lady Stella's plans.

Loona, forced to ally herself with House Goetia, now has to balance her human life and her secret operations for Stella (scouting targets, smuggling artifacts, or sabotaging rival occult groups) while putting up with her new boss's theatrics and the bickering and blundering of her personal hit squad of imps. She bristles at Octavia calling her "pup" and treating her as a pet... and hates that a part of her doesn't mind the nickname at all. Octavia may enjoy watching Loona squirm under the pet names and light touches, but she does value Loona as an asset and wishes to shield her from her mother's worst excesses.