Being a telepath, Charles had access to everything a person could think of. And when living in a mansion full of teenagers, he finds there's a common pattern. Sex and How Are Charles and Erik Doing It God Can We Stop Thinking About This?

After a while, he brought it up with Erik.

"Rope?" Erik repeated.

"Rope and other paraphernalia. Personally, I don't see why we need them to begin with--What's with that look on your face?"

Erik seemed to be deep in thought, "Rope, huh?"

"Erik."

"Oh, you're right, it's a terrible idea," he said calmly, going back to his book, "Not good for a stiff professor at all."

Charles frowned, "Stiff?"

"Stiff."

"I'm not stiff."

"Stuffy, then."

"We are not playing the semantics game," Charles huffed, turning to his side.

Erik just smiled, shark teeth and razors.

The next day, Charles scrutinized the rope when he thought Erik wasn't looking. After that, he felt it out, loop for loop. Finally, he decided he couldn't be all that bad and trying something new was always interesting.

Erik grinned and kissed him so hard that Charles decided a little rope burn would be worth it.

(it was)