Shin'etsu Kisaragi

Shin’etsu is loyal, courageous, and willing to act when formal authorities will not. He volunteers to infiltrate the Kasumiōji compound despite the danger and the absence of official approval.

His investigation also demonstrates trust in his captain. Even after a Bakkōtō takes control of him, he uses his final strength to warn others about the weapon rather than defend his own reputation.

Shin’etsu is a trained First Division swordsman, but the anime does not name his Zanpakutō or show a released form. No Bankai or specialized Kidō technique is attributed to him.

His successful infiltration indicates professional competence, though the mission ends when he is discovered. The parasitic Bakkōtō forced onto him can override his will and direct his body against an assigned target.

When reports emerge that the Kasumiōji clan is manufacturing Bakkōtō, Shin’etsu offers to enter its compound covertly. Gyōkaku Kumoi captures him, attaches one of the parasitic weapons to him, and orders him to kill the person who sent him.

The controlled Shin’etsu attacks Genryūsai Shigekuni Yamamoto, who releases Ryūjin Jakka in self-defense and fatally wounds him. Shūsuke reaches his father in time to hear a final warning about the Bakkōtō, but misinterprets the scene as an unjust execution.

That misunderstanding drives the arc’s revenge plot. After learning that the weapon had controlled his father, Amagai realizes that Yamamoto was not the architect of Shin’etsu’s death.

Shūsuke Amagai is Shin’etsu’s son. His incomplete understanding of his father’s death fuels a long campaign of revenge.

Genryūsai Shigekuni Yamamoto is Shin’etsu’s captain and the intended target of his Bakkōtō-induced attack.

Gyōkaku Kumoi discovers Shin’etsu’s investigation, forces the parasitic weapon onto him, and causes the fatal confrontation.