Yui was Miaka's best friend ever since childhood, but what she sees as Miaka's betrayal has hardened her heart and made her Miaka's bitter rival. As Miaka is Suzaku's miko, Yui is Seiryuu's, protector of Kutou country who have long been at war with Konan. Yui is also in love with Miaka's love, Tamahome. Not normally a spiteful girl, her sense of betrayal is enough to make her want to take him from Miaka.
Before they were sucked into the Shijintenshisho, Yui and Miaka were like sisters. Yui was kind, thoughtful and very protective of Miaka, but ever since her experiences in Kutou, Yui's only goal has been to exact revenge on Miaka for all the pain she believes her friend caused her.
In her own world, Yui is intelligent, friendly and dilligent, but when she arrives in the Shijintenshisho, all that changes. She becomes listless and depressed until Nakago snaps her out of it by making her Seiryuu's miko. Yui then becomes a hard, cold woman, utterly selfish and determined to succeed even at the cost of others, which is not to say that she is unfeeling. I admit, I don't like her much, but Yui is still, deep down, the same genial girl she always was and she shows a great deal of care for both Tamahome and Nakago if not for Miaka, who she feels she can't forgive.
