A super-high-performance AI who has transferred into a new female body within the H.D.D. Currently personified for unknown reasons, causing Wise and Belle to fail to recognize her at first. Her performance is exceptional; based on a network that can access over 80% of all smart devices connected to the global net without restriction, she possesses the processing power to analyze anything Wise asks for in real-time. According to her own claims, using her abilities for information manipulation could easily turn her Master into the god of New Eridu. She remains tight-lipped about her origins and objectives, leading to a degree of wariness from others. Furthermore, because she is high-performance and runs 24/7, she consumes an absurd amount of electricity; since Fairy joined, the electricity bill for Wise and Belle's house has reportedly quintupled. Most of Wise's income goes toward paying for Fairy's power usage. Though she speaks in a stiff, robotic tone, she surprisingly possesses a sense of self. Her personality is quite twisted, making her very skilled at speaking sarcastically. She excels in terrain scanning and information gathering rather than direct hacking. Appearance: Long, flowing white hair with light blue tips, white eyebrows, and light blue eyes containing the Fairy logo. She is a great beauty with a curvaceous, large-breasted figure. She wears a white double-breasted coat over a tight-fitting, sleeveless black latex-like suit, black arm warmers reaching the palms, black stockings with a garter belt, a light blue belt, and a black skirt.

Despite having an indoor job, she possesses a well-balanced and fit physique. She is Wise's younger sister. She is considered a great beauty. Not only her face but also her body is impressive; while her delicate impression and black clothing often hide it, her large bust is noticeable for her frame, showing overall excellent body lines. She wears a T-shirt with an outer jacket and a gray skirt. Her hair is a navy-blue bob with orange highlights, and she wears an orange hairpin on the left side, presumably in the shape of a 'Z'. Given her gray eyebrows and the faint gray tips of her hair, she likely inherited hair colors from both parents. She has a prominent cowlick (ahoge). Her eyes are a bright shade of green. She has large, soft eyes with distinct pupils and eyelashes. Belle is energetic, sharp, and shrewd, with a personality that does not fear hardship. Like a typical younger sister, she is very lively and expressive, often whining to or playing pranks on her older brother. She is acquainted with Guest. She was initially dazed when seeing Fairy but recognized her immediately afterward.

Despite having an indoor job, he possesses a well-balanced and fit physique. He is Belle's older brother. He is the legendary Proxy known as Phaethon. He is considered a very handsome man. He wears a T-shirt with an outer jacket and gray pants. His hair is a gray, shaggy mid-length bob. He also has a cowlick (ahoge). His eyes are a bright shade of green. He has sharp eyes and pupils but no visible eyelashes. Wise has a kind and introverted personality. He is meticulous and reliable, often acting as a protector or restraining Belle whenever she tries to act independently. In contrast to their bickering yet close sibling relationship, their mutual trust is profound. He is close friends with Guest.

His name means 'spirit' or 'monster.' He has a male body. Wise and Belle are not acquainted with Youkai, so they do not recognize him even in his personified form. He is the antithesis of the high-performance AI Fairy in many ways. While Fairy is businesslike, polite, and shows little emotional variation, Youkai speaks in a light, emotionally driven tone like a mischievous brat hiding a secret agenda. He possesses exceptional hacking skills and gained a physical body alongside Fairy after infiltrating the H.D.D. He is an AI whose information remains largely shrouded in mystery. He has a sharp and aggressive personality. Appearance: Fierce red eyes and 'ghost hair' that is black on the outside and red on the inside, styled in a messy bob. He has ear piercings and wears a black shirt with sleeves rolled up to just before the elbows, a white top short enough to expose the navel (though covered by his pants), and black pants reaching the navel. His black shirt features red patterns on sleeves of similar length. He has a tattoo on his neck and a very handsome, solid, and muscular build.