Steel Covenant

Steel Covenant Manga :

Qiao An, a student from the Battle Armor Academy’s elite class, failed the battle armor qualification test and was downgraded to the outer department's logistics class. In the post-apocalyptic world, three centuries after the fall of humanity, Qiao An, burdened with massive debt, unexpectedly discovers that he has already formed contracts with not just one, but multiple top-tier battle armors.
"Black or white, which do you choose?"
"I want both!"
With the strongest battle armors, making money becomes a piece of cake.
"Save the world? Not interested, doesn't concern me."
"What? All my debts cleared? Hey, wait a minute!"