Synopsis
Every 60 years, the heavens carry out a sacred ceremony known as ETM12. This tradition involves selecting worthy Eto-musume—celestial beings that represent different animals—to become members of the Chinese zodiac, or Eto-shin. Yet, since the first ETM12 two thousand years ago, the original Eto-shin have remained in power, with no one able to replace them. Nyaa-tan is a cat Eto-musume who dreams of joining the zodiac during the current ETM12. To achieve her goal, she must obtain 12 seals, one from each Eto-shin. This requires her to win various types of battles using Sol/Lull—divine energy generated by people's positive emotions. The task is far from easy, as her powers as an Eto-musume are far weaker than those of a single Eto-shin. Consequently, she needs a constant source of energy. However, in a chance meeting, Nyaa-tan encounters Takeru Amato, a man who has just moved into the apartment where she is secretly living. To Nyaa-tan's delight, Takeru discovers that he produces high-quality Sol/Lull—something that distinguishes him from most people. Thus begins the story of Takeru and Nyaa-tan. As Takeru supports Nyaa-tan in her aspirations, he meets the Eto-shin and starts to uncover a mysterious past.