Yuka is one of Youko’s classmates in Japan and gets transported to Kou along with Youko and Asano. She enjoys fantasy books and is thrilled to be part of the adventure, believing that she is destined for greatness. Destined to be a rival, she becomes extremely jealous of Youko when she finds out that Youko is the "chosen one" and believes herself to be just as worthy. The king of Kou takes advantage of this to convince her to fight against Youko. She later realizes her mistake after making up with Youko, and Youko sends her back to Japan. In the novels she is only mentioned in passing and doesn't go to the Twelve Kingdoms but remains in Hourai (Japan).

(Source: Wikipedia)