Sōji Okita is a petite young woman with short cyan hair ending at the base of her neck and light purple eyes. She wears the standard Shinsengumi uniform, complete with shoulder pads, hand guards, a waist-cinching belt, and thigh-high leggings reinforced with leg guards. A katana is strapped to her back, her weapon of choice. During an infiltration mission at Minister Ii’s residence, she disguises herself in a coral-colored kimono fastened by a red sash—a garment later torn during a violent confrontation.

Brutally efficient and unflinchingly direct, Sōji demonstrates unwavering loyalty to her master, Hitotsubashi Shigeyoshi, and the Shinsengumi. Her dedication persists even as an unspecified illness erodes her health, driving her to prioritize Shigeyoshi’s safety above all else. She clashes with allies over tactical disagreements, notably advocating aggressive action against Minister Ii despite opposition.

Six months prior to the series’ events, she participated in the killing of Gen’unsai Asai, a dojo owner investigating Shigeyoshi’s affairs. This act establishes her rivalry with Hyougo Asai, Gen’unsai’s daughter. During the main storyline, Sōji infiltrates Minister Ii’s residence disguised as a concubine, aiming to assassinate him upon discovering his plot to trade Shigeyoshi’s Onigami. The mission culminates in a physical and sexual assault by Ii, which she retaliates against before her arrest. She later aids Shigeyoshi in retrieving a critical seal from Ii’s corpse, bolstering his political schemes.

Within the Shinsengumi, she shares a sisterly dynamic with Isamu Kondō and Toshizō Hijikata, though tactical disagreements and clashes over conduct create friction. While she respects Toshizō’s cautious strategies, she consistently prioritizes Shigeyoshi’s immediate protection. Her rivalry with Hyougo escalates into repeated confrontations, where Sōji’s superior swordsmanship prevails. She also faces Maika Yurihara, who disables her Onigami during combat.

A master swordswoman, Sōji swiftly defeats adversaries like Minister Ii and Hyougo. She pilots an Onigami—a towering robotic samurai—deploying its combat prowess in large-scale battles. Her aerial mobility relies on a specialized kite, utilized strategically against both allies and enemies. Her combat philosophy rejects hesitation, emphasizing decisive action even when faced with significant risk.

The series confines her story to its 12-episode run and a canceled 3D film reboot, with no expansion into spin-offs or supplementary media.