Yumi is a 19-year-old yoki-hijo from the sunlit, geothermally active land of Torio. She has waist-length dark hair, light skin, and wears traditional clogs to avoid the hot ground. As a highly Invested individual, she commands primal spirits by mathematically stacking heated rocks. Raised under extremely strict protocols, she feels imprisoned by her responsibilities and privately wishes for a normal life.

Nikaro is a 19-year-old nightmare painter in the perpetually dark, neon-lit city of Kilahito. Pale and lanky with unkempt hair, he goes by the working name "Painter." He initially approaches his job with uninspired apathy, painting only basic bamboo stalks to capture the dark entities threatening his city. Underneath his detached exterior, he is a deeply talented artist struggling with insecurity over past rejections.

Liyun is Yumi's warden and chief attendant. Tall and severe, she enforces the grueling schedule of the yoki-hijo with frequent reprimands and emotional manipulation. She believes strict obedience is necessary for their society's survival and refuses to tolerate any deviation from tradition.

The Father Machine is a complex, multi-legged mechanical device created by scholars from the Institute of Mechanical Solutions. Designed to automatically stack stones and harvest magical energy from spirits, it represents a heavily industrialized approach to the delicate, human-driven art of summoning.

Hoid is a mysterious storyteller who narrates the events of Yumi and Nikaro's lives. Within the world of the story, he spends much of his time magically frozen as a coatrack statue inside the Noodle Pupil restaurant. He possesses significant magical knowledge and provides context regarding the universe's mechanics.

Akane is a nightmare painter in Kilahito who previously considered Nikaro a close friend. She is sociable and fashion-conscious, frequently organizing outings for her tight-knit group of colleagues. When Yumi arrives in their world, Akane immediately takes her shopping and tries to make her feel welcome.

Tojin is a highly muscular young man who works as a nightmare painter in Kilahito. Despite his imposing physical build, he is generally shy and reserved. He is deeply integrated into Akane's social group and shares their complicated history with Nikaro.

Izumakamo, often called "Izzy," is an eccentric nightmare painter in Kilahito. She is fixated on fortune-telling and mystical predictions. Among her friend group, she is the most vocally skeptical and resentful of Nikaro due to his past deceptions.

Masaka is a quiet woman in the Kilahito nightmare painter community who prefers to keep her skin heavily covered. She maintains a mysterious aura but proves to be highly knowledgeable about the planetary environment surrounding the city, hiding a significant secret about her physical nature.

Design is a nonhuman, spirit-like entity running a popular noodle shop in Kilahito. Composed of magical energy housed in an imitation body, she is eccentric, blunt, and possesses the rare ability to perceive Nikaro when he is separated from his physical form.

Sukishi is the bureaucratic foreman overseeing the nightmare painters in Kilahito. He is highly critical of Nikaro's repetitive bamboo drawings and frequently suspects him of slacking off or faking his patrol reports.

Chaeyung is one of the designated attendants serving Yumi in Torio. She facilitates the strict daily routines governing the yoki-hijo's life, handling everything from serving meals to conducting the intricate ceremonial baths.

Hwanji is an attendant assigned to Yumi who previously served a different yoki-hijo. Because of her past employment, she possesses hidden knowledge regarding alternative, less restrictive reform movements within their religious society.