CharactersChizuru Yukimura (雪村千鶴 Yukimura Chizuru)
- Voiced by: Kuwashima Houko
- Chizuru is the main protagonist. She came to Kyoto in search of her missing father, Kodou Yukimura (雪村綱道 Yukimura Kodou), a Dutch-educated doctor who is skilled in Western medicine. Her father is the one who, on orders from the Shogunate, developed the "ochimizu", a potion which increases the drinker's healing abilities, speed, and strength but which also possesses an unfortunate side-effect of turning the drinker into a mindless, vampiric monster. In the beginning of the series, she is seen being chased by two men, who were suddenly attacked by a rasetsu. She witnesses Hajime Saitou kill off the rasetsu and is then taken to Shinsengumi headquarters by Toshizo Hijikata where they allow her to stay, because they too were in search of her father. Chizuru herself also has a secret; she is in fact a pureblood member of the "oni-ichizoku" (the Demon Clan). Chikage Kazama is after her to make the strongest oni. If a pure-blood or the strongest oni mate, they make an even stronger oni; even stronger than their two parents.
- Toshizo Hijikata (土方歳三 Hijikata Toshizo)
- Voiced by: Miki Shin-ichiro
- Hijikata is the vice-captain of the Shinsengumi and makes most of the Shinsengumi's decisions. He is called "Oni-fukuchou" (Demon Vice-Commander) and is both feared and respected by his men. He is also often referred to as "Toshi" by Kondou. Hijikata is the one who brought Chizuru back to Shinsengumi headquarters the night she witnessed a rasetsu on the loose that began to attack two men chasing her. He is responsible for her welfare. He acts as if it is to his dismay but he does care for Chizuru's safety, as he is often shown protecting her during battles. He is based on the historical Hijikata Toshizō.
- Souji Okita (沖田総司 Okita Souji)
- Voiced by: Morikubo Shotaro
- Okita is the First Unit Captain and a brilliant swordsman. He suffers from tuberculosis, and is later visited by Nagumo Kaoru who gives him a bottle of "ochimizu" which he takes so he can "cure" his tuberculosis. Though it appears Okita is later killed in the story, even though he had taken "ochimizu" He is seen in the ending theme in episode 12 on board the boat. From the ending theme footage he appears to be alive, but very weak and in need of help standing; from this we can assume "that medicine" failed to "cure" him. He is based on the historical Okita Sōji.
- Isami Kondou (近藤勇 Kondou Isami)
- Voiced by: Tōru Ōkawa
- Kondou is the commander of the Shinsengumi. He is very emotional and cries easily. Despite this, he has the trust, respect, and loyalty of his men. Later in the story, he is assassinated. He is based on the historical Isami Kondō.
- Keisuke Yamanami (山南敬助 Yamanami Keisuke)
- Voiced by: Tobita Nobuo
- Also known as "Sannan-san" (based on an alternate reading of his surname), he is the bespectacled captain of the Shinsengumi. Both a scholar and a ruthless tactician, he is kind and caring, albeit a bit reserved. After an injury which resulted in him being unable to use his sword arm, he has become cold and suspicious of others. Hope of regaining the use of his arm has led him to drink ochimizu, which he had spent time to research and improve on so the side effects wouldn't kick in; he is the first of the characters introduced to do so. He is based on the historical Yamanami Keisuke.
- Shinpachi Nagakura (永倉 新八 Nagakura Shinpachi)
- Shinpachi is the 2nd division captain of the Shinsengumi. He is usually very cheerful, especially when he is with his comrades. Shinpachi is especially close to Harada and together they often pick on Heisuke. He is very skilled with the sword, but he is also a true alcoholic and womanizer, as he is seen to break curfew one night and was out drinking. He is based on the historical Nagakura Shinpachi.
- Sanosuke Harada (原田左之助 Harada Sanosuke)
- Voiced by: Yusa Kōji
- Harada is the Tenth Unit Captain and prefers the spear to the sword, but he is seen carrying both. He is based on the historical Harada Sanosuke.
- Heisuke Todo (藤堂 平助 Toudou Heisuke)
- Voiced by: Hiroyuki Yoshino
- Heisuke is a young member of the Shinsengumi. He is around the same age as Chizuru. He later leaves Shinsengumi, following Itou along with Hajime Saitou. He too has taken "ochimizu" to recover from injuries. He is based on the historical Tōdō Heisuke.
- Hajime Saito (斎藤 一 Saitou Hajime)
- Voiced by: Toriumi Kōsuke
- Saito is the leader of the third squad and a master of the left hand sword technique. He is silent and a taciturn but also very loyal, polite, and wise. He often analyzes the situation before attacking to figure out which actions are necessary to complete the mission. He is based on the historical Saitō Hajime.
- Kaoru Nagumo (南雲薫 Nagumo Kaoru)
- First seen as a lovely dressed young woman who looks a lot like Chizuru, Kaoru is actually an Chizuru's twin brother (meaning he too is an oni) who was separated from her during childhood. He likes to dress as a woman but is seen as a boy near the end of the story. He also wants to make Chizuru suffer because when they were separated, he was taken in by the Nagumo family who treated him very badly for not being a female oni and that Chizuru forgot about him and that she had a twin brother; he wants Chizuru to feel the pain he had.
- Chikage Kazama (風間千景 Kazama Chikage)
- Voiced by: Kenjirō Tsuda
- Member of the Bakumatsu, enemies of the Shinsengumi. He is part of the Oni clan and is after Chizuru so they can mate and create stronger oni.
