Abara

When a creature attacks the city, a man with strange powers reluctantly stands to fight... but a shadowy government organization has unfinished business with him.
Abara is set in a dystopian world, filled with large structures. The story revolves around creatures known as Gaunas, Gaunas are people who can shape bone like armor and weaponry around themselves through transformation. The transformation begins around the spine and then shapes layered armor. The story focuses on one such Gauna known as Kudou Denji (though he uses Itou Denji as a fake name earlier).

Volume 1: http://www.megaupload.com/?d=NY0KV8W5
Volume 2: http://www.megaupload.com/?d=7FGTBVP1

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