Every 60 years, the skies perform a holy rite known as ETM12. This ceremony entails choosing worthy Eto-musume (celestial creatures representing various animals) to become members of the Chinese zodiac, or Eto-shin. However, since the initial ETM12 two thousand years ago, no one has been able to replace the original batch of Eto-shin. Nyaa-tan is a cat Eto-musume that wants to join the zodiac in the current ETM12. To achieve her goal, she must obtain 12 seals, one for each Eto-shin. To do this, she must win various sorts of combat by utilizing Sol/Lull—divine energy produced by people's good emotions. This mission is difficult, however, because her talents as an Eto-musume are significantly inferior to those of a single Eto-shin.