Mashin Eiyuuden Wataru

Fourth-grader Wataru Ikusabe creates a clay robot named Ryujinmaru and places a mysterious jewel around its neck. Soon afterward, a golden dragon carries him from his ordinary world to Soukaizan, a mountain realm whose once brilliant rainbow has lost its colors under the rule of the evil emperor Doakudar.

An old prophecy names a hero called Wataru as the savior of Soukaizan, and the boy discovers that his clay creation can become a mighty Mashin. Joined by the fearless ninja Himiko, swordsman Shibaraku, and other companions, Wataru climbs through the mountain's strange layers, defeats Doakudar's servants, and tries to restore the rainbow one color at a time.