Shizuku Ninomiya is a Spirit World Warrior and a teacher at Nagatsuki High School, locally renowned for her expertise in combating supernatural creatures called youmu. She engages primarily in skilled hand-to-hand combat, supplemented by her ability to erect Glaciate Barriers for protection and manipulate earth through geokinesis, creating fissures or walls.

She is tall with waist-length light brown hair, often worn loose or in a ponytail, and has brown eyes with a glint of gold. Her typical attire consists of a greyish beige jacket and skirt, a striped blue shirt, black stockings, and shoes.

Shizuku is cheerful, upbeat, and often smiling, though she becomes merciless when defeating youmu. She shows frustration when situations deviate from her plans, especially in romance. She frequently drinks beer in social settings and faces repeated romantic rejections, often attributed to her choice of flashy dresses on dates.

She grew up with Izumi Nase and Yayoi Kanbara, with whom she remains friends. In an idol-themed spinoff, she undergoes a comedic trial presided over by idol judges, charged with "being painful" for her attempts to appear youthful in front of men.

In the main storyline, she tracks and defeats youmu threats, collaborating with other Spirit World Warriors like Hiroomi Nase to address supernatural disturbances. She later participates in confronting significant threats, including instances when another character goes berserk. After conflicts, she resumes her duties as a teacher and youmu hunter, often socializing with Izumi Nase and Ayaka Shindou. Her ongoing single status and occasional frustration over rejections are noted. Her role remains consistent across media, focusing on her professional activities and personal characteristics.