Knights of Sextet

One day, Earth suddenly became unable to obtain metal ore. Robots called "Shiki" were created to wage war in order to obtain it. And separately, there were boys and girls who could become the strongest Shiki by having someone contract with them. However, even such events had not yet reached even a prelude. From one day onward, a boy who changed from a mecha mechanic to a pilot, his female companions, and the Shiki people bring forth a robot & battle & harem romantic comedy. No matter what despair may come, together we will live on.