Friends with Hosuke Sharaku, in the anime "The Three-Eyed One" and also appears in "Black Jack"
Chiyoko Wato (Wato-san) is a character in "The Three-Eyed One" and also appears in Astro Boy as an assistant for Doctor Ochanomizu in the 2003 anime exclusively. She is also in the "Black Jack" series (appearing with Hosuke Sharaku), as captain of kendo club, and is most well-known for being in The Three-Eyed One series.
Chiyoko, in "The Three-Eyed One", is an ordinary school girl. Until the day she meets Hosuke Sharaku, who goes on journeys with her to different locations to fight enemies. She is the sidekick of Hosuke, and her name was actually originated from Watson (from Sherlock Holmes). She provides almost all fan service, from her and Hosuke, in the series.
Originally, Chiyoko was in "The Three-Eyed One", but in "Black Jack" she appears as the leader of kendo club, and is a tomboy (she is generally one anyway). Compares to her best friend, Kumiko Honma, who is also a tomboy. She owes to Hosuke for healing his illness, in the first episode "The Missing Needle", and that's when she becomes a proper friend of Black Jack.