Rui Onda (恩田 累 Onda Rui?) is a retired Toji from Aichi prefecture who studied in Minoseki Academy, and an acquaintance of the school's president Ema Hashima. Currently, she works in Yahata Electronics, a company that works in the development of S-Equipment, as a system developer.
Rui is a bespectacled girl with average-length brown hair and brown eyes. As an office worker, she is often seen wearing typical business attire consisting of a white dress shirt, a black suit and black slacks.
Befitting her friendly appearance, Rui is carefree but mature in handling situations. Despite being aware of her involvement in the pursuit of Kanami Etou and Hiyori Juujou, Rui warmly welcomed the two girls into her house by request from President Hashima, and was not confrontational about their current issue.
Rui originated from Aichi prefecture, and studied for six years total as a middle- and high-school student in Minoseki Academy. She would eventually return her Okatana on March (presumably after graduating from high school) and would be considered discharged from service by the Special Sword Administration Bureau.
After receiving a call from her acquaintance Ema Hashima, Rui wrote a letter to Kanami Etou and Hiyori Juujou, which was relayed through a bag of handmade cookies made by Mai Yanase. Kanami and Hiyori went to the appointed meeting place specified in the note (despite their worries that it was a trap by the Special Sword Administration Bureau) and Rui arrived to take them by car to her apartment unit. Despite knowing about Hiyori's attack on Yukari Origami, she allowed the two to stay for the night, shrugging aside any suspicions from Hiyori.
Kanami and Hiyori repaid Rui's hospitality by cleaning the house and preparing dinner for her. Rui would then show the two girls her computer, where someone by the name of "FineMan" asked for confirmation about their decision to oppose Yukari Origami. As Kanami and Hiyori showed their resolve to continue their crusade against Yukari, Rui's apartment was attacked by Sayaka Itomi, who was present under the orders of President Yukina Takatsu of Renpu Girls' School. Rui was unhurt from the attack, but the conversation between FineMan and the two fugitive Toji was interrupted as they confronted Sayaka. Rui later dropped Sayaka at an undisclosed location away from her apartment after her defeat in the hands of Kanami and Hiyori, and she later made sure that the two fugitives would escape from the increasing activity of the authorities around her neighborhood. Ultimately, Rui was brought into custody, but President Hashima ensured that she would get away from suspicions against her.
Rui, freed from any charges, later traveled to the base of Mokusa, finally revealing her identity as an affiliate of the anti-Origami group. Here, she joined the town festivities along with Kanami, Hiyori and their companions. However, later that night, she joined the girls and her fellow Mokusa members Richard Friedman and Akane Origami to escape a sudden raid by the Special Ritual Riot Squad under Yukari's orders. Although the escape was successful, the raid on the Mokusa base dampened their morale, although they would later recover and devise a simultaneous two-stage plan against Yukari and her forces. After promising to treat everyone for dinner after a successful operation, she watched as Kanami and Hiyori, as well as Mai Yanase, Sayaka Itomi (who defected from Renpu to join Mai), and Mokusa members Ellen Kohagura and Kaoru Mashiko, were launched from S-Equipment pods into the headquarters of the Special Sword Administration Bureau in Kamakura.
- The profile from the Special Sword Administration Bureau database revealed that Rui is a Level 4 certified information technology engineer, a Cisco Certified Architect and passed Oracle Master at Platinum.