Kemono no Joou

Kemono no Joou (獣の女王) is a manga series by Takuma Yokota. It was serialized in Young Ace.

Plot
Once every five thousand years, the twelve beast kings do battle to determine their places in the zodiac. That time has come once again, and the snake king Jaou has chosen Makabe, the "queen" of her school, to be his proxy in the upcoming war.