I Thought You'd Be a Beggar, So How Did You Become the Apocalypse's Overlord?

【Begins as a beggar + everyone is a lunatic + apocalyptic wasteland + urban mind-bender】 Others rely on talent to practice alchemy. I get by picking through trash. They see me as the city's parasite, but I turn around and refine the lofty mastermind behind it all into the perfect “scrap”! Now, the girl who is the apocalypse's only beacon asks me: should I sacrifice her to save the world, or stand against the world for her alone? Tell me in the comments: who should the protagonist's blade strike?