Sakuya, once an assassin for the Dark Killers, entered that shadowed world after killing his abusive father to protect his mother. Betrayed during a mission to assassinate intellectual Shozan Sakuma, he faced arrest and a death sentence.

He possesses pale skin, gray eyes, and long black hair with light blue highlights, typically secured in a ponytail and braids. His attire consists of a black kosode over a white shitagi, bound by a white hakama-himo over black hakama. Light-blue straps secure his zori sandals, and he carries a sword with a blue scabbard, black handle wrap, and golden hand guard and butt-cap.

Sakuya operates with a cool, calculating, and strictly by-the-book demeanor. Professionally focused on efficiency and survival, this approach frequently clashes with Ichibanboshi's methods. Initially, his sole purpose is killing, a mindset forged by his traumatic past.

Recruited from death row by Heisuke Toudou, Sakuya joins six other convicts to replace slain Shinsengumi captains as part of a scheme to restore Kyoto's order. He assumes the identity of Vice-Commander Toshizo Hijikata, forcing collaboration that challenges his solitary nature. While escorting his original target, Shozan Sakuma, Sakuya confronts Hikosai Kawakami, a former Dark Killers associate. Kawakami attempts to reignite their assassination mission, but Sakuya refuses, prioritizing his new role as Hijikata. He kills Kawakami when Ichibanboshi is threatened.

This path forces Sakuya's evolution from isolated assassin to reluctant team member. His choices to spare Sakuma Shozan and protect his Shinsengumi comrades signal a growing duty beyond mere survival. This internal conflict between lethal efficiency and emerging loyalties manifests clearly when he intervenes to save Ichibanboshi in combat.