I'm the Demon King, but They All Call Me a Saint

What are the basic qualities of a Demon King? Looking down at the hordes of monsters prostrating themselves before him, Meng De realized that he had accidentally transmigrated and become a Demon King. The good news: He has immense magical power and can return to the real world whenever he wants. The bad news: The entire Demon King's Abyss is a slum! The monsters live like primitive people, surviving on raw meat and blood! Faced with this awkward situation, Meng De fell silent for a long while, then began shuttling between the two worlds to trade supplies. “An obsolete gas canister?” Wrong! It's an apocalyptic weapon far more powerful than an archmage! “A root that demon creatures use as a chewy snack?” Wrong! It's a thousand-year-old ginseng root, so valuable you can't buy it anywhere! After years of tireless effort from Meng De, the Demon King's Abyss finally climbed out of poverty and prospered. Its standard of living even surpassed that of the neighboring human kingdom. But there's one awkward problem: a Demon King's power comes from doing evil. So how is a good person supposed to replenish his magic? Back in the real world, the upright and kindhearted Meng De began thinking of a solution...