I Open a Shop at the End of the World

Darkness falls and the world ends. Human survivors are eking out an existence in the apocalypse, looking for resources to survive. Ning Xiangyang obtained a less serious system and opened a mysterious store in the apocalypse. "Excuse me, what do you need? Everything except myself is for sale!" Ning Xiangyang smiled. Selling low and selling high, tons of resources made Ning Xiangyang invincible. While others were still eking out an ignoble existence, he was already considering whether to save the world. What? There is a big monster in the north, kill it!