TV-Series
Description
Kyōichirō Yozakura is the eldest son and first child of the tenth generation of the Yozakura family, a legendary lineage of spies. He is a tall, fair-skinned man with short, glossy black hair and often wears a calm, smiling expression. He also operates under the alias Hirukawa, posing as the vice principal of Sakuragi High School, where his youngest sister Mutsumi and her childhood friend Taiyo Asano attend.

His personality is marked by an intense, obsessive, and often comically extreme love for his sister Mutsumi. This fixation stems from a childhood incident in which he accidentally nearly killed her, leaving her with a permanent white streak in her hair. This traumatic event twisted his protective instincts into an all-consuming desire to isolate and safeguard Mutsumi at any cost. He is otherwise a brilliant and composed spy, rarely losing his cool in combat, though his brotherly obsession frequently leads him to treat anyone who gets close to Mutsumi, especially Taiyo, as a dangerous target to be eliminated.

As the family's top operative, his primary motivation is to protect Mutsumi and preserve the Yozakura bloodline. While his methods are often extreme and antagonistic, he genuinely cares for his family and serves as a critical line of defense against external threats. His role in the story is that of a powerful, often intimidating force who initially opposes Taiyo's presence but gradually becomes a reluctant ally and grudging mentor.

His relationship with Taiyo is the most dynamic. He begins by trying to kill him but slowly comes to acknowledge Taiyo's determination and growth, even as he continues to verbally and physically harass him. He shares a complex bond with his siblings, who consider him a pervert for his obsession but still recognize his unmatched skill and leadership. Later, he shows deep affection for Mutsumi and Taiyo's children, designing the basic frames for their protective gear.

Over the course of the series, Kyōichirō undergoes subtle development. While his core personality remains intact, he learns to trust Taiyo more and allows Mutsumi more independence, even if he never fully abandons his overbearing tendencies.

In terms of abilities, Kyōichirō is hailed as a genius even among the extraordinary Yozakura family. He took his first spy exam at age six and forced all other participants to drop out, becoming the sole passer that year. He is an all-rounder, proficient in combat, strategy, and espionage, and his spy rank is Gold. His signature weapon is the Steel Spider, a traditional Yozakura weapon composed of ultra-thin, near-invisible threads that can cut through almost anything. He uses these threads with devastating precision in both offense and defense.