In Japanese mythology , RyÅ `` gÅ `` - jÅ ( ç `` å å ) is the palace of RyÅ `` jin , the dragon god of the sea . In Japanese mythology , RyÅ `` gÅ `` - jÅ ( ç `` å å \/ é 3\/4 å å ) is the undersea palace of RyÅ `` jin , the dragon god of the sea .