Miria Katsuragi, a Youko (fox spirit) serving the Eastern Forces aligned with the Tenko Family, possesses silver hair, red eyes, fox ears, and multiple tails in her true form. She can disguise herself as a human child with black hair, concealing these supernatural features. This disguise was accidentally undone by Koyuzu Shigaraki during an infiltration attempt at the Yuragi Inn. Initially driven by a goal to enter the Tenko Family, Miria identified Yuuna Yunohana as a Tenko and sought to exploit that connection. However, after observing Yuuna's happiness with friends at the inn, she chose not to reveal Yuuna's identity, prioritizing Yuuna's well-being over her own ambitions—a decision reflecting a considerate aspect of her otherwise serious and dutiful personality.

Her background reveals a tendency to distance herself from others due to past experiences where people exploited her Youko abilities. She once encountered Tenko Genryuusai, remembering his spiritual ripple imprint. Miria's relationship with her father is complex; he expressed pride in her infiltration of Yuragi Inn and ordered her to build ties with its residents. Yet, he later manipulated her through hypnosis during the Nadare Arc, using her to weaken the residents for his own gain. After being freed from this brainwashing, Miria confronted him, leaving their relationship strained and unresolved.

Miria transitions from a spy to a reluctant ally. When Yuuna faced pursuit by Ouga Makyouin under suspicions of being Garandou, Miria assisted despite personal risk. She later moved into Yuragi Inn to connect with Yuuna, though an attempt to possess Yuuna failed, indicating a lack of mutual trust. Moved by Kogarashi Fuyuzora's acceptance of her motives and Yuuna's kindness, she began frequenting the inn. A rivalry with Koyuzu involves competitive clashes over transformation skills; Miria is annoyed by Koyuzu calling her a "bakekitsune" yet impressed by Koyuzu's abilities. Kogarashi noted their interactions suggest a genuine, if grudging, friendship.

Her Youko physiology grants transformation techniques, including altering her own appearance, manipulating others' forms, and controlling transformable dolls. Her possession ability requires mutual trust with the host, granting significant power boosts when successful. Unique traits include using maple-shaped leaves instead of traditional tanuki leaves for transformations and hiding her tail and ears more effectively than other Youko. Hiyori Miyazaki addresses her as "Mama-san," finding her ears and tails endearing.

Miria's character arc shows growth from a goal-oriented infiltrator to someone valuing interpersonal connections, balancing her duty to the Tenko Family with newfound loyalty to Yuuna and the Yuragi Inn residents.