A/N. this can be seen as pre-slash or just as friendship.
The first time it happened, Nick was just playing around. Monroe had said something derogatory about Nick's Grimming abilities, and the slighter man had responded by jabbing him in the lower back. It was a soft poke; not enough to do damage but enough to make Monroe growl. Nick grinned in response, and Monroe muttered something in German before carrying on with the dinner preparations as if nothing had happened.
The second time it happened was an accident. Nick and Monroe were chasing a Klaustreich through the woods when it got the drop on them. In the ensuing fight both Nick and Monroe went down, with Nick landing on Monroe. Nick's elbow drove into Monroe's sensitive spot and Monroe howled. Nick scrabbled away and apologised repeatedly. Monroe assured him it was ok and together they tracked down and dealt with the Klaustreich. Monroe had hobbled back to the car, with Nick hovering close to him; afraid to touch the Blutbad. Nick's feeling of guilt was only compounded when Monroe instinctively kept his back turned away from the Grimm for close to a week.
The third time it happened, it was deliberate. Monroe knew Nick was feeling bad about the incident with the Klaustreich days earlier, so when Nick got home from work one gloomy weekday evening, Monroe met him at the door. He explained he'd pulled his back moving a Grandfather Clock. Holding up a jar of salve, Monroe asked if Nick would be kind enough to rub it into his injury. Nick gave Monroe a lopsided smile that told the Blutbad he knew what he was doing, but nonetheless took the jar and instructed Monroe to take off his shirt. Monroe did as he was told and moved with Nick into the living room. At first Nick's touches were timid, but he told himself this was more awkward for Monroe and focussed on the task at hand. Starting at Monroe's shoulders –the furthest point he could fathom from that dreaded spot- Nick pressed his thumbs into the muscles and concentrated on the feel of the knots being released. When there were no more, he moved slowly down and repeated the action until he was mere centimetres away from what he'd mentally been referring to as 'the button'. Taking a moment, Nick took in Monroe's posture. Monroe was so relaxed he was almost doubled over in his sitting position. There was no hint of fear or apprehension, and he didn't even seem to have noticed where Nick's hands were headed next. Nick took a breath and dipped back into the salve. Carefully, he pressed his thumbs either side of Monroe's spine and slid them down. Monroe's intake of breath caused Nick to pause, but the soft mewl that followed pushed him to continue. It took a few more minutes, and Nick would never call the sound Monroe was making a purr out loud, before all the knots were released and Nick no longer had a reason to keep his hands on Monroe's back. Nick pulled away and mumbled that he was done. When Monroe turned to face him, the smile he was wearing settled the last of Nick's worries. Softly he thanked Nick, and Nick brushed it off as expected. They shared a look for longer than was strictly necessary before Monroe awkwardly suggested they put on 'the game'. He didn't know what game was on that night, and neither did Nick, but the TV was turned on nonetheless. Nick retreated to the kitchen momentarily to retrieve some beers, and soon the two men sank back into a comfortable atmosphere.
An hour, and a few beers later, Monroe coughed softly before pointing out that he often did damage to his back; either through hunching over his clock projects for too long, or from moving his cello. As casually as he could manage, Monroe suggested they make this impromptu massage a regular thing. He gave the excuse that Nick was staying with him –rent free- and so it was only fair. Nick hid his smile behind his beer bottle before agreeing to the proposal.