Ruiko Saten is a girl with blue eyes and long black hair with a small, white flower on the left side of her hair. She also prefers wearing medium-sized skirts instead of short ones. Her clothes are known to change multiple times throughout the series with only her school uniform being constant. Her school outfit is a white top with a red ribbon and a blue skirt.
She has an outgoing and friendly personality but is a little shameless as she sometimes flips Kazari's (and only her) skirt in public. At first she displayed apathy towards being a Level 0 but then became envious of the abilities of her friends as she was unable to fulfill her dreams as an esper, as such she used the Level Upper. Later on she grows to accept herself and becomes determined to develop her own abilities, though this has yet to yield any results. Like her friend Kazari, she also has a deep sense of friendship, she was instrumental in helping Kazari and Kuroko make amends and made Mikoto realize that she has friends who she can count on.
She superstitious despite being in the city of science, though she likes to presume otherwise as when she states that she doesn't believe that her mother's good luck charm actually works. Because of this, she is a fan of internet rumors and urban legends, and loves telling her friends about it. This extends to herself, believing that her nose is sensitive to money, though she backs this up by showing Mikoto four bank cards she already obtained. She has a natural tendency to be nosy regarding this, and often gets herself into trouble because of it, often needing to be saved by coincidental events or having become involved in events due to coincidences.
Ruiko Saten can be described as a normal-acting preteen in the series in comparison to her peers. Not having any extracurricular activities like Judgment or being particularly book smart. She is very affable, quick to make friends, and cheerful. She is in the know with the latest trends and fashions, and in fact has the most wardrobe changes the series.
Her ability while using level upper is Aero Hand (lit. "Air Power User"), a power that should allow her to propel objects using ejection points of air, though, she can only move small leaves in the palm of her hands. Once level upper is reversed, her ability level returns to 0.
She also is very athletic, being capable of running for a noticeably longer time than most students during her extra classes after the Level Upper incident, and was capable of quickly reaching the top floor of the large building that housed the Child Errors from the very bottom floor. Armed with a bat, she is able dodge the armed and dangerous Powered Suits attacks and hit them with it.
In the anime original arc of Raligun S she was, along with Kazari, able to memorize an entire manual on how to pilot a giant mecha in a single night and actually be able to apply it in battle. This is exemplified by Ruiko and Kazari easily defeating two mobile weapons. It should be noted that she has not shown any sign of this sort of intelligence anywhere else in the series.
- She displays impressive skill in sewing.
- She and Kazari Uiharu both have cameos in both openings of the first Toaru Majutsu no Index anime, although with shorter skirts.
- Saten appears in the first A Certain Magical Index anime opening despite not appearing in the actual series.