Stoic captain of the Yamainu Squad, charged by the government to capture Orochi's vessel. He is Tenka's childhood friend and Soramaru's swordmaster.
Sousei was born into a family of master exorcists.
According to Taiko, Sousei was separated from his parents at birth and was raised alone. Sousei was isolated as he had no toys or people to indulge him, which greatly explains his gloominess and lack of social skills.
As a candidate for the Orochi's vessel, Sousei joined the Yamainu Squad and began training under Taiko's guidance. The sword Sousei uses is the Abe family's treasured sword, that gets passed down to each generation.
Soon after joining the Yamainu, Sousei befriended Tenka and Kiiko. Sousei also began to reevaluate his belief that he was merely a pawn to capture the Orochi, after he adopted Tenka's dream of being the nation's hero.
To Tenka: "You've always stood above others. But you've decided on your own, and acted on your own. Nobody can follow after you here. Even the exalted sun gets lonely if he can't achieve what he desires. Disappear. High, mighty, and alone."
To Soramaru: "Who said crying was a sign of weakness? It's nothing to be ashamed of. Humans learn to forget so that they can take in all that sadness and suffering. There are moments that only you know. Embrace those memories and cry, before you forget."
To Kiiko: “We can’t have him interfere. Get Tenka away from here.”