|Weapons||Nagasone Kotetsu (katana)|
Kikuichimonji Norimune (katana)
|Manga Debut||Act 56|
|Anime Debut||Episode 31|
|Voice Actor||Tara Jayne|
Seta Sōjirō was the fastest member of the Juppongatana. He was the right-hand man for Shishio Makoto and was usually seen by his side. When not with Shishio, he is off on missions such as assassination or gathering the other Juppongatana. His nickname was "Sojiro the Tenken". He believes in Shishio's philosophy that only the fittest survive. "If you're strong you live, if you're weak you die". His favorite sword was the Kikuichimonji-norimune, which was cracked when he used his Shuntensatsu against Kenshin's Battojutsu. He is the one responsible for the assassination of Okubo Toshimichi .
Sojiro is normally seen smiling, with seemingly no emotion. In actuality, he hides his emotions, making him hard to read in combat, as stated by Kenshin . This ruse is broken when he realizes how strong of an opponent Kenshin is. His true emotions make him appear unnerved, almost insane. However, after the Kyoto Arc, he appears to have calmed down somewhat.
During his time under Shishio's tutlelage and service, Sojiro seems to regard him as a combination of master, god, and foster father.
ChildhoodSojiro was an illegitimate son of a rice business man, and was left in the care of his family brother. Still child, Sojiro was abused and beaten by his family, and he would smile instead of cry to make them stop temporarily. One night, he ran into Shishio Makoto, when he sliced a government official in half. Instead of killing him, Shishio took shelter in a shed and Sojiro would bring him food and bandages. He gave Sojiro a wakizashi to protect himself by killing his family, but he thought being killed by a sword would hurt too much so he hid it under the porch. When his "family" found out Sojiro was harboring a wanted criminal, they planned to kill the boy and turn Shishio in. Sojiro ended up slaughtering the five adults with great speed and strength, the result of believing what Shishio told him; "the strong live and the weak die". Afterwards when he stood in the rain, he seemed to be smiling about it, but he was actually crying. He decided to go with Shishio.
In Rurouni Kenshin
In his first appearance, Sojiro killed Okubo Toshimichi under Shishio's order, his abilities made his presense unnoted. After Kenshin defeated Senkaku, Sojiro travels a fast duel with him, resulting in a tie. Then, Shishio ordered Sojiro bring to him The Ten Swords from the East side of Japan.Sojiro was the last member of Juppontagana that Kenshin must defeat before facing Shishio. He used sukuchi's techniques to move fast enough to hit Kenshin. During the fight, Kenshin made Sojiro to question the reasons that made he be alongside Shishio, and this made Sojiro release his true emotions, allowing Kenshin to predict his moves and discover his advantages. Sojiro got mad, and the battle reaches the climax when Sojiro challenges Kenshin to do a last technique to put an end in the duel, Sojiro used Shuntensatsu against Kenshin's Amakakeru Ryū no Hirameki. The fight ended with Kenshin victorius and leaving the room for face Shishio. Sojiro discovered the key to Amakakeru Ryū no Hirameki and informs Yumi to tell Shishio. Sojiro asks for Yumi return his Wakizachi to Shishio that had once saved him from being murdered. Then, he leaves the Juppongatana and became a traveler, looking for his own truth.
- Shukuchi (Reduced Earth) Sojiro moves at beyond god-like speed, only showing his footsteps crashing into the floor. This also allows him to run on walls. He is also shown to use reduced forms of the technique, naming them (X) steps below shukuchi. Shukuchi is revealed to be the reason why he could keep up with Okubo
- Shuntensatsu (瞬天殺) (Instant Heaven Kill) This is the only attack Sojiro named himself. It involves using Batoujutsu combined with the speed of Shukuchi. It is named for its ability to instantly kill its target victim.