The Four Deities, namely Blue Dragon, Red Phoenix, White Tiger, and Black Tortoise, give birth to successors in every generation whose sole duty is to protect the world of humans from the wrath of the sacred spirits of the Heavenly Realm. These successors utilize the powers of the four sacred spirits to guard the barrier. Before ascending to heaven, they train at Doonggule, a traditional tea house nestled in a quaint country town.