Onsen Musume

Onsen Musume are minor goddesses who live in every onsen. During the day, Onsen Musume go to school in Odaiba, Tokyo to learn how to help more people learn about each Musume's respective onsen, and also to learn special arts that help guests relax and smile.

One day they receive a proclamation from Sunahiko, the god who rules over all of the onsen, commanding them to become idols. The Onsen Musume form idol groups in order to compete in the newly-created idol tournament.

(Source: Wikipedia)