- Chizuru Yukimura
- Chizuru is the main protagonist. She came to Kyoto in search of her missing father, Kodou Yukimura, 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
- 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.
- Souji Okita
- 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.
- Keisuke Yamanami
- 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. Heisuke Todo - Hajime Saito
- Sanosuke Harada
- Harada is the Tenth Unit Captain and prefers the spear to the sword, but he is seen carrying both.
- Chikage Kazama
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.
Heisuke is a young member of the Shinsengumi. He is around the same age as Chizuru. He laster leaves Shinsengumi, following Itou along with Hajime Saitou. He too has taken "ochimizu" to recover from injuries.
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. 
