Metal Back

In the first half of the 21st century, the necessities of a local war gave rise to a new type of soldier with metal surgically implanted in their backs in order to allow them to wear special combat armor. After the war ends and the men are demobilized, people start calling them Metal Backs, a phrase that becomes synonymous with men who have failed to become true heroes... and thus this SF masterpiece begins!

From Manga Reborn