Seta Sōjirō

Sōjirō as he appears in the first anime.

Sōjirō is Shishio's right-hand man, a young assassin trained by Shishio himself. Sōjirō is known for his lack of kenki (offensive aura) in a fight, his apparent emotionless state reflected also in his sarcasm and polite manners with his smile hiding his true feelings. However, he does have a special relationship with Komagata Yumi, who functions as an older-sister figure towards him. Sōjirō usually dresses up in a blue kimono with white handguards.

Born in Kanagawa Prefecture in September of the first year of Bunkyū (1861), Sōjirō is an illegitimate child who was badly mistreated by his father's family to the point of being beaten for faltering in his tasks.[4][5] To build a tolerance to the beatings, Sōjirō put on a smiling face as his tormenters decide to let him be. One night, at age eight, Sōjirō witnessed the recently scarred Shishio Makoto killing two police officers and was spared due to the criminal seeing the boy's smile. While secretly feeding Shishio and providing him with bandages, Sōjirō takes the man's ideals to heart while receiving a wakizashi. When his family learned that he is harboring Shishio and decide to murder the child and pin the blame on the fugitive, Sōjirō uses the wakizashi Shishio gave him to slaughter his family.[5] Soon after, once Shishio's wounds are healed, Sōjirō travels with him as his right hand and member of the Jupongatana.

Sōjirō first appears in the storyline when he uses his superhuman speed to reach and assassinate government official Ōkubo Toshimichi, also killing the official's would-be samurai assassins who would historically take credit for Ōkubo's death nonetheless. Later, after Senkaku's defeat, Sōjirō duels with Kenshin using Battōjutsu with the fight ending in a tie when their swords shattered.[4] Sōjirō is then assigned by Shishio to gather the Jupongatana located in the east side of Japan.

When Kenshin finally arrives at the Room of Reduced Space in Shishio's lair, he finds Sōjirō waiting for him and at first has the upper hand due to his superior speed. But when the confrontation forces Sōjirō to question Shishio's principles, his true emotions surface with allowing Kenshin now able to read his moves and defeat him. Despite his defeat, Sōjirō informs Yumi of the key to Kenshin's ultimate attack while asking her to give Shishio the wakizashi that kept before leaving.

In the aftermath of Shishio's death, Sōjirō becomes a wanderer to find his own truth and ideals. Five years later, he makes his way to Hokkaido where he is reunited with fellow Jupongatana member Yūkyūzan Anji, who was being escorted to Hakodate by Sugimura Yoshie (Nagakura Shinpachi), and joins them.

Sōjirō's shukuchi is fast enough that he can run on walls and instantaneously appear behind Himura Kenshin.

Sōjirō's apparent lack of emotion, his simple, cold-blooded mentality that the strong will live and the weak shall die (弱肉強食, jakuniku kyōshoku, an idiom for "survival of the fittest" or "law of the jungle"), and his skills make him a formidable foe for Kenshin. As a master swordsman of his own style, Sōjirō's abilities have earned him the nickname of "Heaven's Sword" (天剣, Tenken, Ten meaning Heaven and Ken meaning Sword, "Tenken" means swordsmanship of natural endowments).[4] His shukuchi utilizes such powerful speed that, to an observer, it appears that the distance between the two fighters has shrunk (hence the name shukuchi, which means "reduced earth").

During his fight with Kenshin, Sōjirō continually states he's only moving "three steps below shukuchi" or "two steps below shukuchi." While moving at the speed his shukuchi utilizes, the only thing that can be seen is Sōjirō's footsteps ripping through the tatami mats. During "one step below shukuchi", he is able to attack from an omni-directional angle, utilizing not only horizontal but vertical space.[6] While performing true shukuchi, he completely disappears and cannot be seen, even by Kenshin. Sōjirō can dodge the Kuzu-ryūsen (九頭龍閃, lit. "Nine-headed Dragon Flash"),[7] a move which apparently cannot be evaded even by Kenshin himself. Sōjirō is also the first one ever to slash Kenshin in the back in the series.[7]

Sōjirō is also well versed in the Battōjutsu style like Kenshin, as is evident when he decides to use a stance similar to Kenshin's and when he destroys Kenshin's first sakabatō. Combining the true speed of shukuchi with the Battōjutsu, he has created his only named technique, Shuntensatsu (瞬天殺, lit. "Instant Heaven Kill"), meaning "immediate killing by heaven's sword". It is named this because the speed behind the attack is so swift that the opponent not only dies before falling to the floor, but there isn't even time to experience pain. Judging by its appearance in the anime, it appears that the Shuntensatsu is very similar to Kenshin's Amakakeru Ryu no Hirameki, except that it uses speed rather than strength.