Nei Okumura is part of the seventh unit in the Anti-Demon Corps as a rear guard specialist with scouting abilities. She has long pink hair with a headband, blue eyes, and pale skin. In formal settings, she wears a uniform from the Anti-Demon Corps with a red belt and long skirt. During emergencies or breaks, she dresses casually while still being able to operate effectively. Nei is a kind-hearted, diligent girl who gets along well with everyone in her unit, including Yuuki during their first encounter. Despite being young and still in elementary school, she often provides rational advice and exhibits a higher level of maturity than many other members in the Anti-Demon Corps. Her family's reputation granted her early admission into the Corps.
Nei is the only child of Professor Ookawamura, a researcher of Mato, who disappeared due to a Mato disaster which later manifested her powers.