|Title||Sharaku's sister; Black Jack's close friend; Kendo Captain|
|Faction||Oana Senior High School Student|
|Level||Skilled Kendo captain and athlete|
She is a high school girl of average height with short brown hair and brown eyes. She is typically seen wearing her school uniform which consists of a blue jacket over a white shirt with a red ribbon, and a red skirt.
She is a tomboy and also very strong. She is very friendly and protective of her friends and family, coming to their defense or doing whatever is needed to keep them safe and happy. She can be aggressive and argumentative but means well. She can also be bossy, as shown when she tells Sharaku to do his homework and to stand up to his bullies. She is strong willed and very athletic, as shown when she frequently jumps over the school gates and runs to her classes, barely making it on time and well known for her tardiness. She is loud and not afraid to talk back to those who annoy her or to stand up for what she believes is right, showing she has a strong sense of responsibility and justice. She has even been shown to use her skills to ward off bullies from her friend Rei in episode 17 and in episode 46 for her friend Jaw. She can also be competitive and likes to win, and doesn't like it when someone gives her opponent the upper hand or if they cheat.
She is Sharaku's sister. Her father works as an archaeologist around South Asia. She is Kendo captain at her high school and best friends with Kumiko.
She begs Black Jack to save Sharaku's life and is willing to talk to her parents about paying him 50 million and is grateful to him since. She is usually shown at school or at Tetsu's coffee shop or hanging out with Pinoco and Sharaku.
She is the captain of the kendo team at her school. She is also shown to be fairly strong and fairly quick and agile.
- Sharaku: She is very close to her brother and despite the two fighting and her bossing him, the two get along very well. It is implied his crush on Pinoko comes from his close relationship to his sister, as the two have the same personalities. In Osamu's Tezuka The Three Eyed One, Sharaku and Chiyoko are actually love interests of each other.
- Black Jack: She cares a great deal for Black Jack and will often come to his defense when someone insults him. However, she also warns others that he charges ridiculous prices for his surgeries (which is completely true). It is implied she may even have a crush on him because when Chiyoko joked about how Sharaku missed Pinoko, Sharaku blushed and said that Chiyoko has also not been the same and was becoming mopy and depressed since Black Jack left, causing her to blush.
- Pinoko: She is one of her closest friends and supports her friendship with Sharaku, hoping she can whip him to shape.
- Kumiko: Kumiko is her best friend despite the two being polar opposites.
- Tetsu: Despite not much interaction between the two, the two seem to get along well just fine.