Maki Katsuragi is a third-year student at Rinin Academy and a member of the swimming club. She possesses black hair, typically worn long and parted to the side, with red eyes in some depictions or light brown eyes in others. Her physical appearance is slim, pale, and of average height, fitting a teenage build. She is frequently seen in her school uniform—a miniskirt or pleated skirt, sailor suit, pantyhose, and neckerchief—or athletic wear like a one-piece swimsuit or tank top.

Her personality is kind, cheerful, and friendly, enabling her to interact easily with everyone. Close childhood friends Motoko Tamura and Izumi Shinohara treat her like an idol. Despite this outward positivity, Maki struggles with significant family problems, including constant parental quarrels that trouble her deeply. She is the second daughter of Dr. Aiko Katsuragi, Rinin Village's sole physician, and Toshio Katsuragi. Her siblings include older sister Shiori Nakamura and brother Mamoru Katsuragi. The Katsuragi women share a strong family resemblance, appearing as versions of each other at different ages.

A pivotal moment occurs when Maki witnesses her mother, Aiko, participating in a Rinkan Club "ceremony" with multiple partners at the school swimming pool. This event traumatizes Maki, leaving her terrified of sharing her mother's fate as a cult victim. Distressed, she confides in Shiori while crying in the school toilets, expressing her fear of becoming like Aiko. Later, returning home with Shiori, Maki notices her sister appears pale and realizes Shiori is also involved with the Rinkan Club after seeing her in a compromised state. Maki visits her hospitalized mother attempting reassurance, but the cumulative trauma overwhelms her. The following day, her mental state fractures, leading her to accept the role of the Rinkan Club's new shrine maiden.

Maki's relationship with Motoko Tamura evolves from close friendship to romance, and they become an official couple. This connection becomes a vulnerability when new history teacher and yoga instructor Suzuko Yamazaki blackmails Maki, threatening to target Aiko again unless Maki nominates herself as shrine maiden. Maki reluctantly agrees to protect her mother, but the sacrifice proves futile. After Suzuko overthrows Motoko as Rinkan Club leader, she sentences Aiko, Maki, and Shiori to be "shrine maidens for life," ensuring their perpetual enslavement to the cult's rituals, including forced pregnancies. Suzuko declares any future daughters born to the Katsuragi women will inherit this role, cementing generational subjugation. Psychologically broken, the women perceive this eternal torment as an "unishment."

In an alternate storyline from the visual novel's male route, Maki is forced into a relationship with her brother-in-law, Tomonobu Nakamura, under threat of harm to Shiori. Secretly filmed by her brother Mamoru, she becomes blackmail material for Eizou Kajimura, who aims to make Shiori a shrine maiden. A deal is struck where Maki becomes Kajimura's slave instead. With help from Rinkan Club president Nishimoto Kazuma, she volunteers as a shrine maiden and has sex with Kazuma first. This collaboration leads to Kajimura's death and Tomonobu's exposure. Shiori initially reacts with shock but forgives Maki; they share shrine maiden duties and both become Kazuma's lovers.