The story revolves around Eto-shin. "Eto-shin" are the 12 divine messengers chosen from "Eto-musume," or zodiac girls representing all kinds of animals. From ancient times, these 12 divine messengers have protected the land of the rising sun. They are powerful beings who have survived through "ETM 12," a divine tournament held every sixty years, and admired by all Eto-musumes. 
 
Fast forward to now, the present day, and the year ETM 12 will be held. From all over Japan, Eto-shin candidates, or in other words, Eto-musumes gather in great numbers. 
 
Within that group exists a single cat Eto-musume. 
 
Her name is Nya-tan. She is thought of as the one closest to becoming an Eto-shin, but is a misfortunate girl who always ends up undermined by evil rodents. 
 
The only way to become the 12 zodiac signs is to beat all the Eto-shins. However, the power of the Eto-shins is so great, and no Eto-musume has ever won in the tournament for the past two thousand years. 
 
When Nya-tan meets an ordinary high school boy, Takeru Amato, the story begins! 
 
(Source: Anime News Network)