Is a member of YOMI, a bodyguard of Shō Kanō, and a disciple of Akira Hongo though he is not one of the top ten members.
Yami/YOMI Saga
DofD Tournament Arc
Seta and his partner Hayami are ordered by Shō to keep Kenichi Shirahama occupied after he abducts Miu Fūrinji. Kenichi is able to fight them off at first, but eventually his wounds from his fight with Kaku Shin Ten start opening, leaving him vulnerable. As they are about to finish him, Ryūto Asamiya arrives and quickly defeats Hayami with his Seikūken. Angered, Seta attempts to attack Ryūto but is also defeated with a Gungnir.
Sakaki and Hongo Arc
Seta later appears in a black car with Hayami, waiting in the forest near the village where Sho was raised. When his master whistles, he and Hayami both appear to fight Kenichi, both of whom have improved substantially since Kenichi had seen them on Despair Island. Seta has shown the use of Karate that utilizes much grappling, and unhesitantly grabs both of Kenichi's wrists to kick him between the legs. He has shown rage at Kenichi for defeating Sho, and likely harbors a grudge against Miu for being a cause of Sho's death. Both Hayami and Seta are later shown training with what used to be their master's training materials.
The Tidat Kingdom Arc
After Hongo's fight was interupted by Jenazad, he along with Hayami help track down Jenazad and tell Kenichi and his masters of the location to Tidat, Jenazad's kingdom. After arriving to Tidat, they help track Jenazad. Once Hongo kills Jenazad and everything calms down, Hayami and Seta arrive by helicopter and worry over their masters condition and help take him and everyone to Jihan's palace.