She is a Misaka Mikoto clone that appears in both Toaru Majutsu no Index and Toaru Kagaku no Railgun. Originally having a small role in Toaru Majutsu no Index, her character was later expanded in Toaru Kagaku no Railgun. She is the 10031st clone to be produced and killed by Accelerator for the Level 6 Shift experiment, she is also the first clone Kamijou Touma meets.

She looks the same as Mikoto, although for emphasis her eyes are drawn in a different way. Goggles and blue-striped panties are common to all Misaka clones and Misaka 10031 is no exception to this.

She has the same personality as most clones, with emotions that have been suppressed as they weren't beneficial to the experiment. Despite this, she still feels pain and is hurt when Mikoto drove her away when she tried to cheer her up, because of this she was a little saddened.

Another slight hint of personality is shown when behaves seriously when confronting Mikoto and Touma about having "robbed" a vending machine, she seriously recited every legal article that the couple ignored while committing the "felony," expressing disappointment on them for engaging in such activities. Unfortunately 10031's nagging was cut short by Mikoto's aggressive personality which dragged her out of the scene to question her about the situation.

She is killed by Accelerator, and her remains are cleaned up by MISAKA 10032.