Yoshida Shoyo is a gentle teacher who raised many disciples at his private school, Shoka Sonjuku. He has a kind and mild-mannered personality, and while he dislikes conflict, he possesses a deep, compassionate heart that treats everyone equally. He taught Gintoki Sakata, Shinsuke Takasugi, and Kotaro Katsura not only swordsmanship and academics, but also the vital lesson of "how one should live as a human being." To his students, he is a father figure whose teachings and words remain a great source of support even after they have grown. On the other hand, his true identity hides a grave secret deeply connected to "Utsuro," making him a key figure who holds the secrets of the entire story.

Gintoki Sakata is a boy who lost his parents at a young age and survived on the battlefield. Despite possessing sharp insight and high combat abilities, he lived a life of loneliness. During this time, he met Yoshida Shoyo and learned the warmth of family and friends at Shoka Sonjuku. Studying alongside Shinsuke Takasugi and Kotaro Katsura, he was taught not just swordsmanship and academics, but also the importance of caring for others and the value of comrades. His meeting with Shoyo changed Gintoki's life forever, and those teachings have been passed down as his personal convictions even into adulthood.

Shinsuke Takasugi is a boy born into the samurai Takasugi family. He possessed excellent talent for the sword from a young age, but harbored loneliness within a strict family environment. After meeting Yoshida Shoyo and attending Shoka Sonjuku, he forged a solid friendship with Gintoki Sakata and Kotaro Katsura. Because he adored Shoyo from the bottom of his heart and cherished his existence more than anyone else, later events would drastically change his life. In his childhood, he was a boy who cared for his comrades and hid a burning conviction within.

Kotaro Katsura is a serious and intelligent boy. He had a deep understanding of academics and possessed calm judgment, yet he also had a kind heart that cherished his friends. He met Gintoki Sakata and Shinsuke Takasugi at Yoshida Shoyo's Shoka Sonjuku, fostering strong bonds while studying together. He deeply respected Shoyo's teachings and grew up with those philosophies in his heart. Even as a child, he had a strong sense of responsibility and was a principled boy who would take action for the sake of his comrades.

Oboro is the leader of the "Naraku," an assassination unit directly under the Tenshoin Naraku, and is a powerful warrior with卓越した sword skills and calm judgment. He is usually expressionless and rarely shows emotion, but in his heart, he harbors a deep loyalty and complex feelings toward Yoshida Shoyo. While he displays a ruthlessness that prioritizes the mission above all else, he also possesses the resolve to sacrifice himself for his beliefs. His connection to Shoyo and Utsuro is deeply involved in the core of the story, and his way of life significantly moves the fates of many characters.