Ruiko Saten is a Level 0 esper student at Sakugawa Middle School in Academy City. Originally from outside the city, she enrolled with dreams of gaining supernatural abilities, even boasting to her brother about her anticipated powers. Though her mother disapproved, she provided support and a good-luck charm that Saten attaches to her bag. Befriending Kazari Uiharu, both enrolled at Sakugawa, where Saten was classified as Level 0 with no detectable abilities. She developed her signature look: long black hair featuring a small white flower accessory on the left side and a preference for medium-length over short skirts. Her casual attire changes frequently, contrasting with her consistent school uniform. Outgoing, cheerful, and socially adept, Saten forms friendships easily. She exhibits a notable fixation on publicly flipping Uiharu's skirt, a habit exclusively targeting her friend. Initially apathetic about her Level 0 status, Saten harbored repressed envy toward espers, particularly her friends, stemming from her unfulfilled dream. This envy culminated in her using the illegal Level Upper device during an incident where she felt powerless to help. The device briefly manifested her latent ability, Aero Hand—propelling objects via air currents—but only at minimal effectiveness, moving small leaves. Side effects caused a coma. Upon waking, she grappled with guilt for sharing the device with classmates, viewing supplementary lessons as deserved punishment. Over time, she accepted her limitations while maintaining determination to develop her abilities. Saten actively investigates urban legends and internet rumors, a hobby contrasting with Academy City's scientific environment. She claims a "nose for money," citing ownership of multiple bank cards, and retains superstitions despite professed skepticism, such as carrying her mother's charm. This curiosity often leads her into dangerous situations resolved through coincidental luck or external aid. She also demonstrates perceptiveness, deducing inconsistencies during memory-altering events involving Shokuhou Misaki and recalling connections others forgot. Despite lacking esper powers, Saten displays surprising physical prowess: endurance during training, agility evading powered suits, and strength smashing machinery with a baseball bat. Later developments show enhanced capabilities, including infiltrating a prison undetected, scaling walls using specialized gloves, and intercepting threats to protect Uiharu. Her Level 0 status grants unique advantages, such as immunity to AIM-dampening fields like Capacity Down, crucial in disabling anti-esper technology. Saten's relationships define key character aspects. Her central bond with Uiharu involves mutual support during crises like the Level Upper incident. She facilitates reconciliations, such as mending Uiharu's rift with Kuroko Shirai. Unexpectedly, she earns fondness from morally ambiguous figures like Frenda Seivelun and the magician Xochitl. Her friendship with Mikoto Misaka is impactful; Mikoto credits Saten with revealing her reliance on others, and Saten remains the only person to recognize Mikoto as a friend despite memory alterations. Saten actively strengthens group bonds, initiating informal address among peers. Her chronology extends beyond Railgun into broader franchise media. She appears in Toaru Majutsu no Index light novels during the Battle Royale and Freshmen Arcs via cameo illustrations. During Othinus's world reconstruction arc, she discusses clones and urban legends. In the Kamisato Rescue Arc, she prioritizes pragmatic solutions over direct intervention. The Jailbreak Arc showcases her physical growth and loyalty, orchestrating Uiharu's escape and confronting adversaries. She participates in Academy City's evacuation during the Coronzon Arc and appears in the film Miracle of Endymion, relaying information about a kidnapping.