U7, member of Japan Branch of Unicorn, is the one who controls the gigantic Giant Robo with the wrist-watch controller microphone. One day, he receives from his father a parcel as a birthday gift. It is a kit for constructing a man-size robot. But the actual sender of the gift is Professor Gurama whose home is a 4th dimensional nebula. The robot is completed. And, when U7 puts the switch in to animate it, a sudden change comes over the robot. There is, facing U7, another U7, exactly the same self to the last detail. The new U7 grabs the control wrist-watch. Just then, other members of the Unicorn come to see U7, and find two U7s, each claiming that he is the real U7.
