Yui is Miaka's best friend who
later becomes her enemy during the series because she thought that
Miaka had come back into the Universe of the Four Gods to see Tamahome
again, not save her. It later turns out that Nakago was manipulating
her in order for HER to grant his wish of becoming a god (hah! in
the afterlife...). In reality, Yui isn't as mean as we think she is.
She is truly a best friend to Miaka. It was jealousy and lack of attention
was what got her, I think.
"Miaka, who did you just
hit with the desk?"
First episode of Fushigi Yuugi
after Miaka's wild dream ^_^.