Ryōbi is a first-year student at Hebijo Clandestine Girls' Academy, having transferred from Gessen Girls' Academy with her twin sister Ryōna. She is the youngest of three sisters, raised by the eldest, Ryōki, after their parents' death. Ryōbi once idolized Ryōki but grew resentful, culminating in shouting "go die" at her the day before Ryōki perished on a mission—a moment Ryōbi deeply regrets. Her heterochromatic eyes feature a blue left iris and green right iris. She wears a white button-down shirt secured by a belt holding extra-large bullets, a black ankle-length dress, white thigh-high stockings, and red dress shoes. Accessories include a red hairband and a red Native American-style overcoat. During shinobi transformation, her breast size increases significantly, reflecting her ideal self. Extreme sadism defines Ryōbi, often driving her to crave brutal harm, especially toward Ryōna. She reacts violently to criticism about her chest size and seethes with jealousy toward those possessing larger breasts. Yet she exhibits underlying compassion, shown through guilt when accidentally shooting Murasaki or suppressing remorse while battling Imu to reach Miyabi. Mentions of Ryōki's death trigger aggressive outbursts, revealing her lingering vulnerability. In Shinovi Versus, Ryōbi and Ryōna infiltrate Hebijo to avenge Ryōki, believing Miyabi caused her death. During an assassination attempt, Ryōbi targets Imu to prevent her shielding Miyabi, but Murasaki intercepts the bullet. This sparks events leading to the Hebijo group's reconciliation after Ryōki's true demise is revealed. Estival Versus delves deeper into Ryōbi's guilt, climaxing with Ryōki's temporary resurrection during the Shinobi Bon Dance festival. After a battle, Ryōbi embraces her sister, apologizes for her past words, and finds closure before Ryōki's spirit departs. Spin-offs like Bon Appétit! feature Ryōbi entering a cooking competition to win a wishing scroll for larger breasts, fueled by frustration over derogatory nicknames about her chest. In Peach Beach Splash, she voices resentment toward "buxom worlds" during water gun battles while opposing breast-centric ideals. Her combat style centers on a modified bolt-action sniper rifle with an axe head attached to the stock, enabling long-range sniping and close-quarters melee. Ninja Arts deploy area-of-effect explosives like bombs or missile salvos. This versatility excels across ranges, though some ultimate attacks may miss nearby opponents.