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Rokusui River (漉水, Clearwater River) in the Kingdom of En stretches from Sei Province to Gen Province. It empties into the Black Sea in the west of Gen Province. It seasonally floods in autumn, which leaves the ground around it fertile.

During the reign of Kyou-Ou, he breached the original levees, leaving the shoreline inhabitable and neighboring towns defenceless against floods. New settlements and cultivation of the land recently began after Shoryu ascends the the throne, though without levees, the land floods whenever it rains.[1] The Rokusui River becomes the center of attention in the The Twelve Kingdoms: The Vast Spread of the Seas when the river floods the croplands and the current king does nothing about it.

Supposedly, Atsuyu's motives for turning against the king is because the levees have not been rebuilt. However, when the Royal Army is mobilized to build embankments only on the far side of the Rokusui, Atsuyu orders the destruction of the new levees because he believes the king's forces are trying to flood Gen Provincial army. The people of the town of Shineki, outraged that Atsuyu's forces would destroy the levees they have long awaited for, fight back and Atsuyu loses the support of the public.