Chou Robot Seimeitai Transformers Micron Densetsu

On the mechanical planet of Cybertron live super robotic organisms known as Transformers. There, mainly consisting of convoys, the Cybertron army, and their old enemy Destron fell into conflict to gain hold of a new power to join their side. A new breed of Transformers known as the Microns. But, grieving over the battle the Microns set off to the other end of the universe. 4 million years later, on Earth, 3 young children activated a mysterious panel inside a cave. And somehow, that was the dormant Micron...Headmasters starts with Galvatron leading a new batch of Destrons to wage war on Seibertron, the Destron Headmasters. The Cybertrons are rescued by the arrival of the Cybertron Headmasters, led by Fortress (Cerebros, the head of Fortress Maximus). It is revealed that Fortress left Seibertron millions of years ago in search of energy, and have finally managed to come home. He explains that the Headmasters are from a planet called Master; the human-sized robots who live there built themselves Transformers-sized bodies. They can then transform themselves into the heads of the robots, and have now joined the Cybertron-Destron war.