Ryugu-jo, also known as Dragon Palace, is a mythical underwater palace from Japanese folklore. It is said to be the home of Ryujin, the dragon god of the sea. The palace is often depicted as a beautiful, shimmering place made of coral and precious stones, where time flows differently than on land. In the famous tale of Urashima Taro, a fisherman visits Ryugu-jo after saving a turtle. He spends what feels like a few days there, but when he returns to the surface, he discovers that many years have passed. The story highlights themes of time, nature, and the consequences of one's actions.