Since ancient times, Japan has upheld the tradition of the 12 Zodiac signs. Eto-musumes (Zodiac girls), who have the appearance and behavior of the animals of the Zodiac, are pure hearted messengers who act as a bridge between humans and the gods. Every 60 years, the “ETM 12” tournament takes place in Tokyo’s Akihabara district, where aspiring girls from all over Japan gather for the chance to become the next zodiac sign. One of those girls is Nya-tan, a cat girl who was tricked by a sneaky rodent and was not able to become a Zodiac girl. There is only one condition to become an Eto-musume: you must defeat the other 12 signs. But with strength bestowed to them from the heavens above, no one has been able to defeat them for 2000 years.

The story begins when Nya-tan meets Takeru Amano!

[Source: Crunchyroll]

Unaired short specials included in the second through fifth Blu-ray and DVD volumes Etotama.

The seemingly eternal cat-and-mouse battle has ended, and now everyone is living peacefully. One day, an Eto-musume (Zodiac girl) named Na-tan appears, to the puzzlement of the 12 signs, and to the unreserved delight of Nya-tan (whose spirits are always lifted by the pure, straightforward Na-tan). Meanwhile, Chu-tan also appears and warns of a looming disaster. "The seal ... has been broken." Who is this mysterious Eto-musume Na-tan? What in the world is the deity that has awoken beneath the seal?

[Source: Anime News Network]