A former Japanese professional gymnast before petrification, Homura Momiji served as a secondary antagonist within the Tsukasa Empire, acting directly as Hyoga's trusted subordinate. Revived by Tsukasa's forces, she became Hyoga's right-hand operative, executing missions with precision and unwavering loyalty. Her first major action involved infiltrating Ishigami Village during Hyoga's assault. Swimming in undetected, she set the village ablaze, exploiting the distraction of the main attack and forcing the evacuation of villagers, including children and the elderly, without causing fatalities. She then maintained covert surveillance over the village for months, memorizing residents' names, faces, and routines while enduring harsh conditions with minimal supplies. During this time, she accepted Senku's cotton candy, revealing a fondness for sweets despite initial wariness. Detecting the absence of Chrome, Magma, and Gen on a mission to deliver a cellphone, Homura pursued them. She demonstrated acute observational skills by spotting and washing off tungsten powder Senku used to track her. Though she located the group and attempted to destroy their communication device, a coordinated counterattack involving a felled tree and Kohaku led to her capture. She was later freed by Hyoga's ally, Yo Uei, and resumed her duties. Acting on Hyoga's orders after his betrayal of Tsukasa, Homura destroyed the vital chemicals within the Cave of Miracles. Following Hyoga's defeat and capture, her retaliatory attack on Senku resulted in her own subdual and imprisonment alongside him. Both remained confined until the Treasure Island expedition, where Kirisame petrified them off-screen using the petrification device. After the Kingdom of Science's victory on Treasure Island and their voyage to America, Hyoga negotiated their revival to train the Kingdom's fighters, insisting Homura be included. She subsequently joined the Kingdom of Science alongside Hyoga, her primary loyalty to him remaining evident. She contributed practically as the navigator aboard the Perseus and later fought alongside Kingdom members against threats in America, such as alligators, showing particular enjoyment of François's hamburgers. During the conflict with Dr. Xeno's forces in South America, Homura participated in efforts to reclaim the petrification weapon. In a critical moment against Brody, she leaped to catch the keys needed to activate the device but sustained a shotgun blast to her arm, causing her to drop them. Despite her injury, the mission succeeded, activating the weapon and petrifying her in the global beam. She was later revived in America by Taiju and the Kingdom of Science. Homura possesses notable speed, agility, and gymnastic maneuvers that make her difficult to apprehend despite limited strength. She demonstrates strategic intelligence, exploiting village vulnerabilities and deducing Senku's tracking powder, alongside high endurance in extreme cold and free diving. Her personality combines calm detachment, acute observation, and fierce loyalty to Hyoga, gradually integrating into the Kingdom of Science's operations while maintaining her core allegiance. A recurring character note is her susceptibility to sweets like cotton candy and vanilla ice cream, contrasting her typically serious demeanor.