Break Blade

Broken Blade or Blake Blade (ブレイク ブレイド, Bureiku Bureido) is a Japanese manga series written and illustrated by Yunosuke Yoshinaga. Flex Comix published the first tankōbon volume of the manga on April 10, 2007. An anime series released by Production I.G & Xebec on april 2014.

Plot
Rygart Arrow is the only one in his world who lacks the inherent ability to power up quartz, the energy source that makes all of the machines run. Nevertheless, he's pretty well connected. The King and Queen of his country of Krisna happen to be old college friends. But so is Zess, the guy who is leading the army of a neighboring kingdom in an attack on Krisna.

How did it comes to this? There's little time to ponder the implications as an army in giant, mechanized battle suits attacks. Arrow just feels like he's in the way - until he comes across a powerful, ancient mech that no one has yet to be able to figure out how to run. But his natural affinity for the suit's operating mechanism may just turn Arrow into the most important player of all.