Riku: Shizu's loyal servant and constant companion on his travels. It seems Riku provides counsel to Shizu, and is content with staying beside Shizu and letting him decide the course of their journey.
King Yukio: Shizu is the only son of King Yukio and the unnamed queen.
Unnamed Mother (death by suicide)
Unnamed Grandfather: Shizu ends up taking his grandfather's crown with him as a momento when he leaves the Coliseum.
Kino: Shizu's relationship with Kino is one of mutual respect as skilled combatants and as a fellow traveler. Shizu is grateful to Kino for ending his revenge quest and his family's legacy for patricide. When they meet up again even though they had initially chosen different sides, Kino opts out of killing Shizu and instead teams up with him to overthrow another country's tyranny.
Tifana "Ti": A little girl that Shizu meets in Ship Country. She is initially sent as his guide in the new country and speaks quite little. Over time, she warms up to Shizu and Riku and later joins them on their adventures.