Nei Ōkawamura, an 11-year-old girl, serves as the youngest member of the Anti-Demon Corps' Seventh Unit. Her parents vanished in a Mato disaster, leading to her adoption by her great-aunt, the prominent Mato researcher Dr. Ōkawamura. This connection granted her early access to a Peach, bestowing supernatural abilities despite her youth. Nei balances her duties with elementary school in Kochi Prefecture, traveling via a gate in the corps dormitory. She maintains hope her parents are alive and that her powers might locate them, reflecting persistent optimism. Physically, Nei possesses bright white skin, long pink hair often secured with a headband, and blue eyes. Standing 145 cm tall, she wears the standard Anti-Demon Corps uniform with a red belt and long skirt for formal meetings. During casual or emergency situations, she dons simpler age-appropriate attire. Her personality blends kindness, diligence, and unexpected maturity. She politely welcomes Yuuki Wakura to the Seventh Unit dorm, frequently assists him with chores, and openly acknowledges her youth to set boundaries. Nei displays thoughtful insight, offering reassurance when Yuuki is distracted by personal concerns and praising his contributions. She actively strives to improve her housekeeping skills, accepting Yuuki's guidance in this area. While generally composed, intimate moments, like giving Yuuki a reward kiss, cause visible fluster. Nei's primary ability, "Promise," is a rare clairvoyance detecting entities within roughly five kilometers, aiding in locating Mato disaster victims or identifying Shuuki threats. Physical contact during its use allows others to share her vision, utilized for real-time intelligence in combat. When borrowing Yuuki Wakura via Kyouka Uzen’s Slave ability, Nei triggers a unique transformation named "Slave: Sparkling Stars." This form dramatically enhances Yuuki’s senses, granting X-ray vision through solid objects like walls or clothing and auditory perception sharp enough to detect heartbeats. The reward needed to maintain this state is notably mild due to her age, typically an affectionate head pat or brief cheek kiss. Within the Seventh Unit, Nei shares mutual respect and camaraderie. She fosters a supportive bond with Yuuki Wakura, appreciating his housework efforts while receiving his encouragement. She regards commander Kyouka Uzen with deference, following orders promptly during missions and training. Interactions with Shushu Suruga reveal underlying tensions; Shushu interprets Nei and Yuuki collaborating on chores as romantic rivalry. Nei fulfills critical non-combat roles during operations. She provides reconnaissance by scanning the Mato for Shuuki incursions or dimensional gates, alerting the unit to threats like craters harboring Shuuki nests. At the exhibition match against the Sixth Unit, she cheers enthusiastically in supportive attire but avoids direct combat. When enemy commanders breach the match, she evacuates safely with Ginna Bizen, later using her Promise ability to let Ginna observe the battle remotely. Nei also participates in unit training, testing Yuuki’s transformations and adapting to the unexpected sensory effects of the Sparkling Stars form. Her personal quest centers on an unwavering commitment to finding her missing parents, a resolve strengthened by hearing accounts of contact from Mato disaster victims. Additional details include her ranking in series popularity polls (5th and 8th) and her role in educational segments explaining Mato-related concepts. Her surname combines characters meaning "great," "river," and "village," while her first name translates to "peaceful."