Minami-ke OVA bundled with the 10th volume of the manga.

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?

In a world plagued with malicious ghosts, how is it possible to combat the existence of such evil spirits? The answer is to hire a "Ghost Sweeper"—a professional exorcist, whose duty is to exterminate any unwanted ghoul or poltergeist. When it comes to Ghost Sweepers, Reiko Mikami is considered to be a cut above the rest. After receiving an offer to examine a haunting near Jinkotsu Hot Spring, she sets off to put her skills to work. Accompanied by her assistants, the underpaid and perverted high school student Tadao Yokoshima and the friendly teenage ghost Kinu Himuro, GS Mikami details the wacky exploits and adventures of these three as they go about investigating paranormal activities. [Written by MAL Rewrite]

The anime centers around a boy named Kouta Kouka (Kouka Kouta in Japanese name order, an apparent wordplay on Coca-Cola). Kouta strives to be the world's best Bottle King at the Bottle Battles in the virtual Drink World. He comes across his Bottleman partner Colamaru and then wages battles with various rivals. (Source: ANN)