Yukari Uchida, Hitomi's best friend, is 15
years old. She's track manager, and frequently complains about Hitomi's
lack of punctuality. She's very caring though, and advises her friend on
many things.
Yukari, having been associated
with track like Hitomi, also met Amano. And, like her best friend, fell
for him as well. However, she kept her feelings for him a secret, even
from a certain tawny-haired girl. I 
think
she did this so as not to cause rivalry between them and to keep their
friendship secure. Hitomi managed to figure it out much later after looking
at a photograph taken at a track meet a few years before. The picture shows
her, Yukari, and Amano, but it's obvious that Yukari is trying to steal
furtive glances at the handsome brunette.
We all know that Allen
and Amano share similar looks and the same voice. This is probably what
pushed Hitomi ever so closer into becoming infatuated with the dashing
blond: she saw her high-school crush in him, and was desperate to have
some connection, no matter how small, to her life back home.
Yukari and Millerna,
though not alike physically, shared the same voice in the Japanese version.
Like the situation with Allen, Millerna's similarities to Hitomi's best
friend might have been what caused her to become friends with her and forget
her jealousy. The english version didn't have this, so those of us who
saw that version were simply lacking of a tiny explanation that doesn't
vouch for that much anyway.
Yukari appeared only
three times in the series. In episode 1 (Fateful Confession), Episode
15-cut(The Guided Ones) and Episode 21 (Fateful Decision).
In episode 1 she was voiced by Willow Johnson (you may also recognize her
from Cardcaptors: she played one of Clow Reid's minions), and in the other
two she was voiced by Saffron Henderson (also played Eriya/Naria). I think,
but I'm not sure, that Yukari in A Girl in Gaea was played by Saffron.
In the Japanese version of Esca, Yukari's voice actor remained the same
throughout the entire series. She remained Yukari in the movie and also
played Sora. She gave up her role of Millerna to another though.