Sakagami Shuzen, a primary antagonist and Iga ninja, orchestrated the invasion and conquest of Fushikage Castle, leading to the deaths of the Yuki family, including Jyutaro Yuki's father. This act became the catalyst for Jyutaro's quest for vengeance.

Shuzen harbored profound envy and resentment, particularly within the Mogami clan where he served as a martial arts instructor. His animosity toward fellow retainer Asano Shigenari arose from perceived differences in etiquette and favor. Blinded by this resentment, Shuzen ambushed and murdered Asano Shigenari in 1547, an event preceding the main story yet significantly impacting its course.

After seizing Fushikage Castle, Shuzen employed strategic deception for protection, including using a kagemusha. This tactic misled Jyutaro during an infiltration for revenge; Jyutaro initially believed he killed Shuzen, only to discover he slew the decoy. Shuzen's sister, Hotarubi, acted as his loyal enforcer. When Jyutaro confronted Shuzen directly, Hotarubi intervened, severing Jyutaro's right arm and nearly killing him. Kagemaru's intervention saved Jyutaro and resulted in Hotarubi losing her own hand.

Following a successful rebellion led by Kagemaru and Jyutaro against Fushikage Castle, Shuzen escaped. He later resurfaced under the alias Rozan Daizen Toshitaka, hiding in Fushimi, Kyoto, demonstrating his adaptability. Shuzen further infiltrated powerful circles by assuming the identity of Akechi Mitsuhide's body double, aligning himself with figures like Oda Nobunaga.

His fate culminated in a confrontation with Jyutaro Yuki, who tracked him down in Kyoto with authorization. During this encounter, Jyutaro achieved his vengeance by decisively killing Shuzen.