Shinobu Kobayashi captains her academy's swim team, possessing neck-length red hair and brown eyes. She maintains an innocent facade around teachers but exhibits ruthless cruelty when unsupervised. Academically accomplished as a straight-A student, she harbors arrogance and envy, particularly toward swim teammate Miyuki Nonogusa after Nonogusa replaces her for a school swim meet. Kobayashi is perpetually accompanied by her subordinate Mikimoto, who obeys her without question. Kobayashi and Mikimoto corner Nonogusa in the locker room, binding her hands and feet with tape and gagging her. Kobayashi physically assaults Nonogusa, commands Mikimoto to violate her with a vibrator, slices her swimsuit with a knife, and photographs the assault with a Polaroid camera for blackmail. Mika Ito and her boyfriend join the harassment, escalating it into an orgy involving Nonogusa. Later, Kobayashi and Mikimoto fall victim to an arousal spell cast by student Taki Minase during swim practice, compelling them into sexual acts with each other in the locker room. Minase photographs them for coercion. In one storyline, after Minase exploits Nonogusa, Kobayashi retaliates by joining nurse Reika Kitami in torturing Minase. Kobayashi urinates on Minase while Mikimoto performs oral sex on him, and Nonogusa assaults him with a vibrator. Prolonged torture combined with aphrodisiac injections results in Minase's death from exhaustion. Another storyline depicts Minase trapping Kobayashi in the art room. After she insults him, he threatens her with a wine bottle previously used for paint thinner storage. She attempts escape but is restrained by another student, tied to a desk, and penetrated with the bottle until unconscious from pain. Mikimoto and Nonogusa later revive her. In the Bible Black universe, Kobayashi participates in a mass orgy in the school basement during events of the game sequel *Bible Black: The Infection*. Appearing dazed and consumed by lust, she is freed when Minase places a talisman in her mouth, breaking the spell and rendering her unconscious. She is hospitalized alongside other victims. Her role in the anime *Bible Black: Only* reiterates her involvement in Nonogusa's locker room assault and the ensuing orgy, consistent with her game portrayal.