うなぎ

A white female ferret that can transform into a humanoid hybrid; she is the only notable such hybrid of its type in any form of literature. In her humanoid form, Unagi is indistinguishable from a normal human except for her white tail and animal ears. She does not get along with Mii at all as Mii becomes jealous of the time she spends with Chris.

From url=http://en.wikipedia.org/wiki/List_of_Popotan_characters#Unagi.