Rebuild World, Volume 1 (Rebuild World #1-4)

Hunters brave the ruins of a long-dead civilization at the behest of the corporate city-states who thrive on its detritus. Amidst the decay lie powerful artifacts of ancient technology, eclipsing anything the corporations can develop. For a few successful hunters, the search for these relics is a road to untold riches. For most, it's a shortcut to slaughter at the hands of mutant bioweapons and robotic sentinels. And for those trapped at the bottom of society, it's the only way out.

Akira is uneducated, underfed, and unprotected - just another homeless kid in the sprawling slums between the walls of Kugamayama City and the deadly wastelands which surround it. Relic hunting offers his only hope of clawing his way to a better life outside the slums. But his first, desperate foray into the ruins threatens to end his brief life - until he meets a mysterious, incorporeal woman named Alpha.