In a world where Mecha Girls rule, Caesar Leat was nothing—F-rank trash, written off by everyone. Then the Upgrade System awakened. A dying Mecha Girl became his first masterpiece: SSS-rank, born from scrap and sheer grit. Now he's climbing, one upgrade at a time. But power doesn't go unnoticed. The Mechanicus, the shadowy elite pulling strings from the top, thinks they're untouchable. They just haven't met a guy who turns junk into legends. And his Mecha Girls? They'd burn the world for him.