Break Blade Series by Yunosuke Yoshinaga

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. Good thing the King and Queen of his country of Krisna happen to be old college friends! But so is Zess, the leader of the army of mechs invading Krisna. As usual, Arrow feels useless in the face of battle, until he comes across a powerful, ancient battle suit that no one else can run... moreRygart 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. Good thing the King and Queen of his country of Krisna happen to be old college friends! But so is Zess, the leader of the army of mechs invading Krisna. As usual, Arrow feels useless in the face of battle, until he comes across a powerful, ancient battle suit that no one else can run. His natural affinity for the suit's operating mechanism may just turn Arrow into the most important player of all. less

When the resources of of oil have run dry, the people of Krishna start using their inner strength to generate energy. However, 25-year-old Arrow hasn't been able to develop the ability, so he's known as an "Un-sorcerer." One day, when Arrow meets his old friends, King Hozuru and Queen Shigune, and they share the news that a neighboring country has invaded their country with an army of Golem (robots) led by their old friend Zess... moreWhen the resources of of oil have run dry, the people of Krishna start using their inner strength to generate energy. However, 25-year-old Arrow hasn't been able to develop the ability, so he's known as an "Un-sorcerer." One day, when Arrow meets his old friends, King Hozuru and Queen Shigune, and they share the news that a neighboring country has invaded their country with an army of Golem (robots) led by their old friend Zess. As Hozuru shows Arrow the big Golem that he uncovered recently, but hasn't been able to operate, the city comes under attack by Athens' army. At the same time Arrow accidently stumbles into the command center of the broken Golem's brain and it mysteriously powers up!Meanwhile, Arrow's home of Krishna is also being invaded by Athens. Whey can Arrow now operate the Golem and why is Zess attacking his old friends? less

When the resources of of oil have run dry, the people of Krishna start using their inner strength to generate energy. However, 25-year-old Arrow hasn't been able to develop the ability, so he's known as an "Un-sorcerer." One day, when Arrow meets his old friends, King Hozuru and Queen Shigune, and they share the news that a neighboring country has invaded their country with an army of Golem (robots) led by their old friend Zess... moreWhen the resources of of oil have run dry, the people of Krishna start using their inner strength to generate energy. However, 25-year-old Arrow hasn't been able to develop the ability, so he's known as an "Un-sorcerer." One day, when Arrow meets his old friends, King Hozuru and Queen Shigune, and they share the news that a neighboring country has invaded their country with an army of Golem (robots) led by their old friend Zess. As Hozuru shows Arrow the big Golem that he uncovered recently, but hasn't been able to operate, the city comes under attack by Athens' army. At the same time Arrow accidently stumbles into the command center of the broken Golem's brain and it mysteriously powers up!Meanwhile, Arrow's home of Krishna is also being invaded by Athens. Whey can Arrow now operate the Golem and why is Zess attacking his old friends? less