Youko

Youko is a Kyuubi no Kitsune (Nine tailed fox) that appears in Monster Musume: Everyday Life with Monster Girls Online.

Zoological Classification
Kyuubi no Kitsune (lit. Nine-tailed Foxes) are a psudeohuman race that appear in Japanese folklore as intelligent beings that possess magical abilities to shape shift. While some folktales speak of kitsune of wildly different moralities employing this ability to trick others, other stories portray them as faithful guardians, friends, lovers, and wives. It is unknown if male Kitsune exist (as Kitsune can use both genders in their shapeshifting abilities) or if they are a single-gendered race.

It is said that the more tails a kitsune has (they may have as many as nine) the older, wiser, and more powerful they are. Because of their potential power and influence, some people make offerings to them as deities.

Trivia

 * A Kyuubi no Kitsune, or Nine Tailed Fox, is said to be the final form of the Kitsune. In most myths a Kitsune's mystical power is based on how many tails they have, making the Kyuubi no Kitsune the strongest variation.
 * Youko's name is one kanji change away from being "Demon Fox" (妖狐).