Ryuu

The northernmost kingdom of the Twelve Kingdoms, Ryuu is one of the four "central" kingdoms and borders the Black Sea along with En and Kyou. The capital city is known as Shisou. In episode 21 of the anime, Enki describes the kingdom of Ryuu as mysterious and is troubled by his uncertainty of the country’s status. Rakushun is sent by Enki to investigate and a friend of Rakushun later claims that Ryuu is prosperous. According to Rakushun, it is also one of the few kingdoms with a prince; Enga (淵雅), the current prince of Ryuu, is the kingdom's Daishikou, the chief minister of law.

The kingdom of Ryuu has very strict laws and it is said that the last king of Hou had modelled his laws after those in Ryuu. The current king of Ryuu, Jo Rohou (助 露峰, Jo Rohō), has ruled for 120 years, but there are signs the realm is in decline. The ministers and officials willingly accept bribes; they agree to take the jewels Shoukei had stolen from the king of Kyou as a bribe. It is speculated that corruption in Ryuu extends all the way to the king of Ryuu. Youma also infest Ryuu's shores. During his investigation, Rakushun concludes that Ryuu is collapsing.

The buildings and cities of Ryuu are small and simple and most are located underground to protect inhabitants from the seasons.