The teacher of Shoka Sonjuku and the mentor to Gintoki, Takasugi, and Katsura. He is the one who found Gintoki and brought him into the school, and he possesses a gentle personality. While he has a somewhat eccentric side and power far beyond that of a normal human, his fundamental kindness is evident in how he takes in abandoned children and runs a school for free.

A child who was picked up by Shoyo and came to live at the school. Rumors circulated that he was a corpse-eating demon, and among Katsura and Takasugi, he is arguably the strongest (for the sake of survival). He has natural silver perm hair and dead-fish eyes. He finds everything a bother and rarely pays attention in class, but he seems to follow Shoyo in his own way. He is the only one who calls Shoyo by his name instead of Shoyo-sensei. He calls Katsura 'Zura'.

The sole heir to the Katsura family. Before his only grandmother passed away, she told him that the quality of a true leader is to survive until the end even if it means running away in a pathetic manner, a lesson he keeps deep in his heart. He was set to receive a scholarship at a prestigious school based solely on merit rather than money or connections, but after a chance encounter with Gintoki and Shoyo, he had a great realization and joined Shoka Sonjuku. He speaks with a refined, noble tone and retorts, "It's not Zura, it's Katsura!!" whenever he is called Zura.

A boy from a wealthy family and a childhood friend of Katsura Kotaro, having attended the same school. Feeling frustrated with a school system built only on connections, he meets Gintoki and Shoyo and joins Shoka Sonjuku, prepared to be disowned by his family. Initially, he visited under the pretext of a dojo challenge just to beat Gintoki, but the moment he defeated Gintoki for the first time, he discovered true joy and entered the school. He is the shortest among the three and is often called 'Chibisugi' by Gintoki. He calls Katsura 'Zura'.