Tank Knights Portriss

Around the three Fortress Knights and a human boy named Yuma who are about to shape the Fortress Planet, known as the home where robots live in peace. But the harmony was disrupted because of the sudden presence of a dictator Dark Fortress along with his evil schemes. Now it's up to the Portriss Knights and Yuma, who accidentally got into the Fortress Planet, to battle the evil forces maintain peace throughout the Fortress Planet.

Super sadly this is the only one of its kind