Reinhard is transported into the world of Overlord. First Fanfiction

Subaru Natsuki has escaped the hellish loop that was the White Whale and the Witch Cult's devious machinations toward his loved ones. Now with a new goal ahead of him, Subaru has ventured with Sebas and Demiurge into the Sorcerer Kingdom where the Overlord himself awaits to greet him.

Subaru Natsuki or Renald, as he was known in-game, was one of the most accomplished players of Yggdrasil. Once it was announced, that the game will be shutdown, Subaru thought that he would have to return to the "real" world and once again suffer the reality of a shut-in NEET. But destiny and a certain silver-haired witch had other plans for him...

At his most desperate and most broken down after being rejected by all of the royal candidates, Subaru Natsuki seems yet again destined for another terrible fate. But a mere moment before his misfortunes consumed him, Subaru finds himself being offered aid the most unlikely of sources. Not a knight, not a hero of destiny, but a butler, and a devil.

Separated from his home and family, a certain butler must figure out his strange new situation, and possibly a way to get back. Before any of that though, he's gonna need a new job...

Overlord x RE:Zero crosover what do you ecpect