Ryobi is a shinobi student who began her training at Gessen Girls' Academy alongside her twin sister, Ryona, before transferring to Hebijo Academy. She is the younger twin and the youngest sister to Ryoki. Following their parents' death, Ryoki raised both twins. Ryobi deeply admired Ryoki as a child but later grew resentful and envious, particularly of Ryoki's physical attributes and abilities. This culminated in a final confrontation where Ryobi screamed at Ryoki to "go die" the day before Ryoki left on a mission from which she never returned. Ryoki's death left Ryobi burdened with lasting guilt and regret. Visually, Ryobi possesses heterochromatic eyes: her left eye is blue, her right eye is green. Her typical attire consists of a white button-down dress shirt belted at the waist to hold oversized bullets, worn over a long black ankle-length dress. She wears white thigh-high stockings and red dress shoes. Accessories include a red hairband, a red overcoat reminiscent of Native American clothing, and a black ribbon tied in her hair resembling bunny ears. Personality-wise, Ryobi exhibits overt sadism, finding motivation in inflicting pain and insults, often targeting Ryona. She harbors a pronounced complex about her breast size, reacting with intense hostility to any criticism. Despite her cruel tendencies, she demonstrates underlying compassion and remorse, such as when she accidentally shot Murasaki or expressed guilt after defeating Imu. Mentions of Ryoki frequently trigger violent reactions. Her backstory drives her actions in "Shinovi Versus," where she and Ryona enroll at Hebijo to infiltrate Miyabi's trust and assassinate her, believing her responsible for Ryoki's death. During the assassination attempt, Ryobi targeted Imu first to prevent her from shielding Miyabi. Murasaki intercepted the bullet, resulting in her apparent death. This event triggered Imu's "Root of Calamity" power, leading to Ryobi and Ryona's defeat. The sisters later reconciled with Miyabi's group after learning the truth about Ryoki's demise. In "Estival Versus," Ryobi's breast complex evolves into a fixation on hip size. She declares herself the leader of a "hyper booty" movement, claiming the largest hips among the Hebijo Elite. She coins phrases like "Death to all big busts!" and "Booty Land," framing her physical attributes as a new ideological path. She recruits Yomi as her "rival" in spreading "hyper booty battles," symbolically replacing established heroines like Asuka and Homura in this self-proclaimed revolution. The spin-off "Bon Appétit!" further explores her breast size insecurity. She rants about the prevalence of large-breasted women, blaming a divine power for her physical appearance. Resolved to win the game's "wishing scroll" to enlarge her breasts, she vows to end derogatory nicknames like "chopping board" or "washing board." During the cooking tournament, she confronts Shiki about her revealing attire and dismisses the practicality of small breasts for sniping. In combat, Ryobi wields a modified Karabiner 98k bolt-action sniper rifle with an axe head attached to the stock, employing it for both long-range sniping and close-quarters melee strikes. Her fighting style balances potent melee combos that repel targets with powerful ranged shots capable of guard-breaking or unbalancing opponents. Her ninja arts include area-effect bomb blasts ("Ricochet Prelude"), frontal explosive attacks, and summoning a missile launcher backpack for multi-salvo assaults. These techniques excel against groups but may miss close-range opponents using evasion tactics.