Joe, a skinny, not-too-great knight, is confronted by a sage who says that the end of the world is coming, and it is his destiny to save it. The only problem is that Joe isn't too fond of his medieval-fantasy style world, and he doesn't feel like working his butt off to save it. So he makes his way to the nearest sorcerer. The sorcerer agrees to transport Joe to another world, the dimension that Earth lies in, for a price. The only trouble is that he won't name the price; instead, he not-so-delicately hints that Joe really should save his own world.
Our protagonist doesn't listen. He is sent to Earth to live in a small city. Soon, he finds out that the price of his cowardice is very high. He is constantly haunted by the ghosts of his previous world. The game begins with Joe living in an apartment in the city, working as a cashier, trying to cope with fear of the ghosts and guilt from his past. Suddenly, he recognizes a customer - it's the sorcerer who sent him to this world. He confronts the man, asking if there's any way he can make up for what he's done. The sorcerer smiles, and Joe blacks out.
Joe wakes up in very disturbing city that he hardly recognizes as his own hometown. It has been invaded by...uhh...aliens, and they have captured the humans of the world. The humans are now slaves. Joe makes it his quest to save the people he cared about, and is aided by the ghosts that once haunted him on the way.
Okay, I know that's kind of messed up and not too original, but it's kind of interesting. Also I just made it up off the top of my head.
