Seito

was once a member of the Twelve Guardian Ninja. He was killed ten years prior to the start of the current storyline, fighting against the members of the attempted coup d'etat.

Background
While he was still alive he was part of the Twelve Guardian Ninja. When six of the members tried a coup d'etat he alongside Asuma Sarutobi, Chiriku, Kitane, Tōu, and Nauma fought against them, only to be killed by Kazuma when Seito and the three later of the 12 Ninja Guards tried to use Limelight on him.

Fire Temple Filler arc
During the beginning of the filler arc is his, Kitane's, Tōu's, and Nauma's corpses stolen by grave robbers, and later revived using lightning. After being revived they were all four approached by Asuma who had figured out the scheme of the robbers. There he tries without luck to stop the later three who seems to have become mindless puppets. He started waking towards an unknown point emitting large amounts of lightning, only to arrive and prepare his part of the limelight technique. When Kitane was killed by Asuma Sarutobi, Kazuma's plan failed and he decided to release the summoned Nauma, Tou'o and Seito.

Abilities
He has an elemental affinity for lightning. When in the the four cardinal directions can he, Kitane, Tōu, and Nauma use a jutsu called Limelight to destroy everything within that area to ash.