Yuko Kisaragi is Professor Ochanomizu's assistant in the 2003 Astro Boy anime. She is the niece of detective Wally Kisaragi, and is usually seen with Momo, her robot ostrich and personal computer. In the English dub, her last name is changed to "Kisagari", stemming from an accidental misspelling on a script.
Yuko is a hard-working woman in her early-to-mid 20s who helps Dr. Ochanomizu with his work. She is very faithful to deadlines and schedules, often having to remind Ochanomizu of his own. Her role in the series is as a foil to Ochanomizu and Astro, giving Astro and Zoran advice and occasionally accompanying them on adventures.
As a child, Yuko spent a lot of her time living and being schooled in Antarctica, where her late father Richard (Yuzuru in Japanese) was working on the Cronos Project. This was an endeavor to get satellite footage of the Cronos solar system. As a child, Yuko was friends with the bulky service robot AR-1, but she called him by the human name Gulliver. However, after Gulliver went missing, his loss changed Yuko's father, and missing Gulliver and observing the change in her father made Yuko grow up to be protective of her loved ones.
Yuko's family also includes the robot ostrich Momo and her uncle Wally Kisaragi. For Yuko, Momo is a combination of a pet and a mobile computer, and Yuko cares a lot about her. Yuko regards her uncle as boisterous and slightly embarrassing, but still worries about his safety.
SeriesYuko is a new character exclusive to the 2003 series. In Astro Boy: Omega Factor, the Tezuka character Wato appears as Ochanomizu's assistant instead of Yuko. However, Yuko is not based on Wato, especially since Wato and Sharaku from The Three-Eyed One appear in the 2003 series with their original Tezuka designs.
The only other series that Yuko appears in is the Pocket Jeunesse book series. She is still Ochanomizu's assistant, but she now treats Astro and Zoran like an older sister or aunt.