Keiko Yukimura (雪村 螢子 Yukimura Keiko), or Kayko Yukimura as she is known in the English anime, the English video games, and the English trading card game, is a character of the anime and manga YuYu Hakusho.

Keiko is voiced by Yuri Amano in the original Japanese anime and both the Japanese and English versions of the Yu Yu Hakusho: Poltergeist Report movie. In the English FUNimation anime Kayko is voiced by Laura Bailey .

Keiko, who is 14 at the start of the manga, has been the childhood friend of Yusuke Urameshi since elementary school. By the time they are students at Sarayashiki Junior High School, Yusuke is a juvenile delinquent and the toughest pupil at school, while Keiko is a straight-A student and her personality is the opposite of that of Yusuke's. This doesn't stop their friendship; Yusuke and Keiko are closer to each other than they would like to admit. Keiko's parents run a ramen restaurant.

After Yusuke was hit and killed by a car, he was allowed to come back to life on the condition that someone kissed him. Keiko kissed him and revived him.

Yusuke tries to not get her involved with his spirit detective escapades. But first Hiei of the Evil Eye kidnaps Keiko and slashes her with a sword that slowly causes a third eye to open. He then lures Yusuke into his lair. Yusuke defeats Hiei with Kurama's help while Botan keeps Keiko's third eye from opening. Keiko is given an antidote and is unaware of what happened.

Keiko finally partly learns what her boyfriend is doing during the Four Beasts story arc. After the other three are killed, the last beast, Suzaku, plays a whistle that sends humans hypnotized with roundworm monsters (a.k.a. makai insects) after Keiko to kill her. Botan protects her and buys Yusuke enough time to destroy the whistle and to kill Suzaku and his bird friend, Murg (Murugu).

She had Botan explain it to her after the ordeal is over, however Botan did not explain it all to her mainly for safety reasons, but she would find out the rest during the Dark Tournament (the Ankoto Bujutsukai or Black Martial Arts Tournament in the original Japanese) when she would go there with Botan and Kazuma Kuwabara's older sister Shizuru.

Since then, Keiko supported her boyfriend in the adventures he goes on. Yukimura literally means snowy village and Keiko means firefly girl. Keiko's birthday is January 31. Her blood type is A, and her hobbies include cooking and cleaning.