Murata Tetsuya was a swordsmith living in Edo. He was the son of renowned swordsmith Murata Jintetsu, and brother of Murata Tetsuko. He was the creator of the Benizakura bio-mechanical sword, which was based on his father's original Benizakura, as confirmed by Tetsuya's sister in Episode 59. He had severe hearing problems, and often spoke like he was shouting. He helped Takasugi Shinsuke by providing him the sword he had made, but didn't care for Takasugi's plots or ambition.
Mitsuba is Sougo's older sister, and took care of him since their parents passed away when they were children. Sougo cares deeply for Mitsuba, and is uncharacteristically polite and docile when around her. She is acquainted with the rest of the Shinsengumi, and regularly brings them extra-spicy senbei, which she herself enjoys. She suffers from tuberculosis, and often requires medical treatment, which Sougo used to send money for. She has romantic feelings for Hijikata. Although it is revealed that Hijikata does in fact love her, he feels that he is unable to give her happiness, that is why he treats her coldly. She dies in chapter 132 of the manga (Episode 87 for the anime) after a brief conversation with her brother. She is roughly based on Okita Mitsu, sister of Okita S�ji. Historically though, it was Okita S�ji who suffered from tuberculosis.