Characters
The series follows the exploits of the three leads−Fuu, Mugen, and Jin−when they are drawn together by circumstance and end up traveling together to find the sunflower samurai. The main cast was created by Watanabe, who wanted a cast of heroes who were silly, immature, and dangerous, with "a touch of insanity". He described Mugen and Jin as unconventional people not bound by the rules of the period. The characters were designed by Kazuto Nakazawa, who had worked as both an artist and director on multiple projects including Ashita no Nadja and the anime segments of Kill Bill: Volume 1. The early character drafts were more to Nakazawa's tastes than the wishes of the production team, resulting in numerous redrafts based on requests. The voice recording included sessions with all three leads together, which caused occasional tensions due to their different work backgrounds.
Mugen (無限（ムゲン）) is a vagrant outlaw from the Ryukyu Islands who uses self-taught sword techniques. Having lived a harsh and solitary life since childhood, he has a deep mistrust and disdain of authority and lives to fight strong opponents. Watanabe thought of Mugen as young and "a little stupid", putting him in stark contrast with Cowboy Bebop protagonist Spike Spiegel. He also described Mugen as symbolizing "a rapper's ideal" of self-expression. Mugen's Ryukyuen origins formed part of Watanabe's focus on inclusivity and tolerance within the narrative. He is voiced in Japanese by Kazuya Nakai. His performance changed little from the audition, someone on the edge who did not follow rules. His performance reportedly improved during the soundchecks, which had a more relaxed atmosphere and emphasis on timing. In English, Mugen is voiced by Steve Blum.
Jin (仁（ジン）) is Mugen's antithesis, a calm and stoic ronin wandering Japan after being forced to kill his master and consequently wearing glasses to disguise himself. He is the best at sensing danger, and prone to risking his life to prove his worth. He is a master of mujushinken, a style of kenjutsu created in the early Edo period by Harigaya Sekiun. Jin was created as a foil for Mugen to stop the story from becoming one-dimensional. A scrapped idea of Watanabe's was for Jin to be an anarchist, but otherwise his personality and design changed little during production. He is voiced in Japanese by Ginpei Sato, at the time a stage actor who had not done voice roles previously after failing auditions for two other projects; his failed audition for Wolf's Rain prompted a staff member to recommend him to Watanabe. He had to learn about voice acting on the job, including timing and getting into character, and during recording for later episodes got into trouble due to wanting to shift his portrayal of the character. In English, Jin is voiced by Kirk Thornton.
Fuu (風（フウ）) is the one who brings Mugen and Jin together to help her. She is a cheerful and spirited young woman and a jack-of-all-trades due to her constant changing between part-time jobs, starting the series working as a tea waitress; she has a pet flying squirrel called Momo. A recurring gag is Fuu temporarily becoming fat after eating a lot, due to her being a big eater. Out of the three characters, Fuu's personality changed the least from Watanabe's original series concept, though her character design underwent major revisions to become more conventionally beautiful. She is voiced in Japanese by Ayako Kawasumi. Compared to her other roles, Kawasumi was asked not to overact her effort sounds outside scenes where her character was very expressive, making her more realistic. It was the first time she did not create a separate internal character to voice Fuu, being asked to be herself as far as possible. Her favorite episode was "Stranger Searching" when the fat Fuu first appeared, as she found voicing this version a challenge. In English, Fuu is voiced by Kari Wahlgren.
In the original plan, there were three semi-regular characters that would appear through the series. They were Rekku, a Dutchman claiming to be Japanese; Koku, a traveling priest acquainted with Jin's past; and Sara, a female ninja who falls in love with Mugen. While their roles were reduced to one-off appearances, versions of the characters survived. Rekku became the character Joji in "Stranger Searching", the priest appeared in "Lethal Lunacy", while Sara was a central character in "Elegy of Entrapment". An early antagonist is Ryujiro, the son of a corrupt government official who loses his arm to Mugen in the opening episode and later plots revenge against them. Historical figures or character homages also appear, for example painter Hishikawa Moronobu; Joji, who is a fictionalized version of Isaac Titsingh; a version of American baseball player Alexander Cartwright; and Ando Uohori, who is a direct reference to Andy Warhol.
