Ryo Shiranui, an A-Rank Assault student at Tokyo Butei High, carries himself with unwavering politeness and elegance. His pre-academy background stays largely concealed, though peers quickly recognized his firearm expertise during a first-year bank robbery mission. There, he calmly neutralized the assailant leader with precise leg shots, never dropping his characteristic smile—an action that sparked his friendships with Kinji Tohyama and Gouki Mutou. Shiranui presents a kind, demure personality, avoiding the spotlight yet earning trust as reliable. He supports friends readily but deflects personal inquiries about himself. A playful streak surfaces occasionally, like collaborating with Mutou to send an embarrassing text to Aria H. Kanzaki from Kinji’s phone. Despite popularity among female students, he has never pursued romance. Kinji notes Shiranui wields two distinct smiles: one for charming others and another reserved during Butei operations. His primary firearm is an unsuppressed Heckler & Koch Mk.23 MOD.0 pistol, supplemented by an unspecified knife standard for Assault students. Peer-dubbed "Old Hand" for marksmanship, he maintains absolute composure while hitting targets with effortless precision—likened to "tossing rubbish into a bin." He also handles diverse firearms adeptly, including a USAS-12 shotgun deployed early in his tenure. Beyond guns, Shiranui excels in close-quarters combat via Assault training; Kinji admits besting him would prove difficult even in Hysteria Mode. Additionally, he masters stealth and tracking, demonstrated when he covertly followed Kinji onto a train after Kinji left the academy. Shiranui actively engages in Kinji’s social circle. Prior experience secured him a midfielder role in a school soccer match. Later, he discreetly boarded Kinji’s train during Kinji’s period of contemplation about leaving Butei High, offering quiet support.