Satsuki Miyanoshita was born in May 1990. At age eleven, she moved from Tokyo to her deceased mother Kayako Miyanoshita's hometown with her father Reiichirou Miyanoshita and younger brother Keiichirou Miyanoshita. Her mother died when Satsuki was five, thrusting her into significant household responsibilities and care for Keiichirou, including cooking and homemaking tasks. This role shaped her strong protective instincts, especially towards her brother. Standing approximately 4 feet 9 inches tall, Satsuki has fair skin, bright green eyes, and reddish-brown hair usually worn in a braid secured with a pink bow. She typically wears a red jacket with cream-colored sleeves, a pink undershirt, a blue skirt, white socks, and black shoes. Following repeated accidental exposure incidents due to clumsiness, she adopted wearing shorts under her skirt. Her physical appearance draws comments from peers regarding perceived lack of conventional femininity, though she bears a strong resemblance to her mother in both looks and mannerisms. Initially doubting the supernatural despite early encounters, Satsuki gradually accepted ghosts' existence after discovering her mother's Ghost Journal in an abandoned schoolhouse. This journal documented Kayako's experiences sealing hostile spirits, and Satsuki shouldered the duty to confront entities released by urban development. She learned to strategically use the journal's knowledge, identifying spirits' weaknesses and employing quick thinking over innate spiritual abilities. This transformed her from skeptic to determined exorcist, culminating in overcoming limitations by channeling her mother's guidance beyond the grave to defeat the entity Ohma. Her personality blends maturity and volatility. She exhibits a strong sense of responsibility, managing household duties while shielding Keiichirou from distress, often steeling herself against fear to appear resilient. Yet she displays irritability, particularly reacting to Hajime Aoyama's persistent harassment involving skirt-flipping and derogatory remarks about her appearance. She responds with physical threats, snarky retorts, and aggressive outbursts, though her underlying care for friends and family surfaces during dangerous situations. Relationships define key aspects of her journey. She maintains a close bond with her father and acts as both caregiver and occasional bully to Keiichirou, whose vulnerability and bond with the cat-possessed demon Amanojaku complicate her protective role. Her dynamic with Hajime mixes antagonism with mutual reliance during supernatural threats, hinting at unresolved tension. She forms a steadfast friendship with Momoko Koigakubo, who provides psychic connections to Kayako, and works alongside classmates Hajime and Leo Kakinoki despite their recklessness. Amanojaku, initially hostile, develops allegiance to Satsuki and Keiichirou over time. Satsuki's background as a descendant of the Kamiyama bloodline contrasts with her lack of inherent psychic powers, requiring her to rely on intelligence, the Ghost Journal, and collaboration to seal spirits. Her development arose from reconciling human limitations with her legacy, ultimately leveraging her maternal connection to achieve peace.