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 my...