Fable: Against The Fall Of Tomorrow

The Demon Lord Won.

Three centuries ago, Demon Lord Ragnor united Demonkind and invaded the overworld. Heroes rose to stop him. They got defeated. For the first time in recorded history, a Demon Lord conquered a nation and kept it. The world has lived in that aftermath ever since — heroes, resistance groups, and smaller nations pushing back while the Royal Demon Force (RDF) keeps expanding. Generations pass. Nothing changes.

Elliot doesn't know any of this yet. He's an aspiring fantasy author from Earth who just wanted to share his story — he dreamed of it becoming someone's favorite, of bringing something new to the isekai and fantasy genre. Until he met his demise in an accident. He wanted to die in peace, but an entity named Selena dragged him out of it and forced a long-term contract on him.

The terms: turn a three-hundred-year losing war in humanity's favor by toppling Demonkind's twelve Heroes and clearing the path for humanity. 

It sounded impossible. Selena simply called it his job.

His enemies aren't just strong. They're in a league of their own.
If he wants to live, he'll think his way through it — surround himself with strong companions, learn how this world actually works, hone his magic and combat skills, and become the biggest headache to the Royal Demon Force.