Keiko Yukimura, or Kayko Yukimura in the English anime produced by FUNimation, English video games, and the English trading card game is a straight-A student whose personality is opposite that of Yusuke's. Yukimura literally means snowy village and Keiko means firefly girl, or respectful child. Keiko's birthday is January 31. In the series, her blood type is A and her hobbies include cooking and cleaning. Keiko's parents run a ramen restaurant called the Yukimura Diner. She is 14 at the beginning of the series and 18 at the end.

After Yusuke is hit and killed by a car, he is allowed to come back to life on the condition that someone kisses him, and this ends up being Keiko. Yusuke tries to not get her involved with his spirit detective escapades, though interferences from Hiei and the Four Beasts prevent this. Keiko asks Botan to explain Yusuke's scenario to her after the ordeal is over. Botan instead does not explain it all to her mainly for safety reasons and instead tells her an almost unbelievable lie, though Keiko believes. Keiko finds out the rest during the Dark Tournament when she goes there with Botan and Kazuma Kuwabara's older sister, Shizuru. Since then, Keiko supports her friend in the adventures he goes on, staying by their sides during the Sensui arc for moral support along with Shizuru.

Yusuke and Keiko, who are childhood friends, are closer to each other than they would like to admit. Towards the end of the anime, Yusuke stops by her parents ramen restaurant and proposes to Keiko. It's a really tender moment until her father interrupts, saying how Yusuke always used to do that whenever Keiko got upset with him. She doesn't really say anything, but Yusuke doesn't need it to know she has accepted, and Keiko spends the next three years studying hard in a famous all-girls school, called Dai-ichi School for Girls in the English anime. At the end of the anime, after a meeting with the major part of her friends, Keiko finds herself looking at the beach. She then screams at the sea, "I'm tired of waiting for you, Yusuke!" He then shows up next to her unexpectedly saying "I don't want you to wait either," She is in shock, yet jumps onto him and hugs him, bringing him to the ground. As she stares into his eyes, she kisses him, showing that even after Yusuke made her wait for so long, she still loves him.