Blue Dragon, Red Phoenix, White Tiger, and Black Tortoise.
To stop the sacred spirits of the Heavenly Realm wreaking havoc in the world of humans, successors of the Four Deities are born in each generation to guard the barrier with the Heavenly Realm, using the powers of the four sacred spirits. And the place they gather to train before they ascend to heaven is Doonggule, a traditional tea house in a small country town.