Hirumi Hishigata, a student at Seiin High School in Academy City, wore her long hair in twin tails and the standard school uniform. She possessed the esper ability Information Circuit, enabling her to manipulate the perception and recording of information. This power rendered herself and others unnoteworthy to observers and degraded the quality of any retained data about them. During her life, she befriended Esther Rosenthal, who was assisting Hirumi's brother, Mikihiko Hishigata, in his neuroscience research focused on enhancing esper abilities through physical reinforcement. Hirumi died prior to the main series events. Esther later resurrected her using Rosenthal-style necromancy. This resurrection resulted in Hirumi's body becoming possessed by Taowu, an ancient evil spirit housing the will of Isaac, an ancestor of the Rosenthal family. Mikihiko remained unaware of the possession, believing his sister had been restored. Throughout most appearances, Hirumi was largely silent and physically inactive, frequently depicted connected to wires and pipes within a laboratory. Both she and Mikihiko were affiliated with the rogue Anti-Skill faction Disciplinary Action (DA), exploiting the organization solely to advance their personal goal of achieving a "perfect mind and body." This plan specifically aimed to elevate Hirumi to Level 6, requiring the capture of Last Order or another Misaka Sister to serve as the core for a weapon designed to facilitate Hirumi's ascension. As events unfolded, Esther confronted Mikihiko with the truth about Taowu's possession. During this confrontation, Mikihiko intercepted Esther's attempt to exorcise the spirit using Emperor Shun's Blade, sacrificing himself. This sacrifice, combined with the completed installation of an esper-enhancing formula into Hirumi's body, triggered Taowu's full manifestation. The entity discarded its imitation of Hirumi's personality, revealing its true nature and motives. In the aftermath, moments before the constructed body housing Taowu underwent a catastrophic collapse, the genuine consciousness of Hirumi briefly surfaced. She acknowledged her brother's sacrifice and bid him farewell before her physical form disintegrated. Beyond these events, Hirumi appeared in the mobile game *Toaru Majutsu no Index: Imaginary Fest*, temporarily revived alongside other deceased individuals during the in-game event "The Return." She also made a brief appearance in the crossover short *Tobidase Ippou-san Hachamecha Kaishingeki*, encouraging her brother during a challenge.