|Relatives, etc.||Haruki Tachikawa (Brother)|
|Anime debut||Episode 1|
|Manga debut||Chapter 21|
|English Voice||Terri Doty|
Yuko is an average-sized teenage girl with shoulder-length brown hair that has bangs hanging over her eyebrows, brown eyes light-green square-rimmed glasses and a warm expression.
She is often seen wearing her school uniform.
Yuko is a kind girl who cares about her friends as seen when she wanted Shinichi Izumi and Satomi Murano to patch things up. She enjoys teasing Satomi about her crush on Shinichi. Though she may become easily infatuated, as she quickly became attracted and started drawing pictures of Hideo Shimada. She even tried to talk him out of killing people to no avail.
She is clever enough to plan around Hideo's abilities in case he turned out hostile, discarding cutting or crushing tools in favor of a bottle of chemicals for her self-defense.
- The name Yuko means "abundant, rich, plentiful" (裕) (yu) and "child" (子) (ko).
- Yuko's surname Tachikawa means "standing" (立) (tachi) and "river, stream" (川) (kawa).
- The Parasyte -the maxim- anime series gave Yuko a more prominent role in the series, introducing her much earlier and had her appear throughout the series.
- In the manga, she was only shown during the Hideo Shimada section of the series. She was not in Shinichi's circle of friends and had no romantic interest towards Shimada.
- Yuko is the only full-blooded human in the series to survive direct conflict with a parasite.