Mimori Tōgō, originally named Washio Sumi, is a central figure recruited by the Taisha organization two years prior to the main events alongside Nogi Sonoko and Minowa Gin to fight Vertex threats. Her exceptional aptitude led to adoption by the influential Washio family. As Washio Sumi, she wielded a bow and arrow in battle. Tragically, activating her Mankai power twice exacted severe physical tolls: first sacrificing the use of her legs, then losing several months of memories. Following these events, the Taisha returned her to her birth family under the pretense of a traffic accident causing her injuries and amnesia, restoring her birth name. As compensation and partly due to Yuuki Yuuna's high Hero aptitude, the Taisha provided her family a house adjacent to the Yuuki residence.

She attends Sanshu Middle School as a second-year student and is a member of the Hero Club. Preferring her surname Tōgō, she presents a mature and intelligent demeanor while readily voicing her thoughts. She possesses skills in computer programming, maintains the Hero Club's website, and excels at baking sweets. A fervent enthusiast of Japanese history and culture, she avoids non-Japanese cuisine and English loanwords. While self-identifying as a pessimist prone to dark thoughts when isolated, she also displays moments of lightheartedness. Her appearance features long black hair typically tied in a low ponytail with a blue ribbon and dark green eyes. Initially wheelchair-bound due to her sacrifices, she later regains the ability to walk.

Her Hero form wears a blue and white bodysuit with detached sleeves and wields four long blue ribbons extending from her shoulders for mobility and support, compensating for her paralysis. Her arsenal, granted by fairy companions, specializes in ranged combat: Aobozu provides a sniper rifle, Gyobudanuki supplies twin reverse-grip shotguns, Shiranui offers a mid-range pistol, and Kawabotaru creates portals emitting autonomous lasers. Her Mankai transformation manifests as a massive flying gunship with laser cannons. Utilizing Mankai extracts permanent bodily costs; her initial sacrifices were her legs and memories, and during later battles, she lost hearing in her left ear.

Her relationship with Yuuki Yuuna is profoundly close, rooted in their status as neighbors and best friends since Yuuna welcomed her to the neighborhood. Tōgō harbors romantic feelings for Yuuna, though these remain unreciprocated consciously. Her past connections with Nogi Sonoko and the deceased Minowa Gin, forged during their time as Heroes, were erased from her memory until Sonoko later revealed the truth about the Hero System and the Shinju, restoring her memories and allowing their friendship to resume, causing significant emotional turmoil.

Within the Hero Club, she initially provides ranged support during battles. Witnessing Yuuna in peril compels her to overcome hesitation rooted in her disability, leading her to transform and fight directly alongside her friends. She grows increasingly suspicious about the true costs of the Hero System after experiencing bodily function loss post-Mankai. During the events of The Great Mankai Chapter, she plays a critical role in breaching the barrier surrounding the Shinju to reach Yuuna, who had absorbed the Shinju's power during the Shinkon Ceremony, an action pivotal to the final confrontation against the Heavenly Gods.

Following the conflict's resolution, which restores her legs and hearing alongside other Heroes' lost faculties, she joins Yuuna in ventures beyond Shikoku years later, exploring Japan's other islands to search for survivors. Her character arc encompasses recovery from profound loss and trauma, the reclamation of her identity and past, and an enduring commitment to protection and companionship.