Pour Some Sugar On Me

Erik moves in to his new apartment only to find that his neighbour is a very promiscuous young lad who moans down the building every other night.

It's hard to get any work done and even more sexually frustrating for him. He has no idea who this young lad is except that when Erik meets him, he's gonna give him a piece of his mind.

And then he does meet him, and his name is Charles. And Erik doesn't quite know how to react.

The AU where young 19 year old Charles is adamant on getting into Erik's pants.