Something that always amused John was Sherlock's back. For a man with an almost blemish free face and arms, he had constellations of freckles on his back, hidden by shirts and jackets.
The first time John had seen Sherlock without his shirt, his attention had been elsewhere, i.e. Sherlock's chest, where the suspect they'd been chasing had caught him with a knife. It was only after; when he went to change the bandages that he had noticed them. John had giggled and prodded one or two with his finger, before Sherlock frowned and pulled away, muttering about being ticklish.
The second time John saw Sherlock's back, once again, he hadn't thought to look. Or rather, he had been too preoccupied with the other parts of Sherlock that required his immediate attention. It was only when he woke the next morning and Sherlock had still been asleep, that John really had a chance to study the freckles properly.
Sunlight streamed through the blinds they'd been too lazy to shut, casting a faint glow on Sherlock's hair, showing the red highlights he always denied were there. John sat up carefully, so his bed mate didn't stir. Sherlock snuffled and pressed his face into the pillow, mumbling John's name, and then fell back into whatever dream he'd been having.
John watched Sherlock's back rise and fall with each breath for a few moments. He was living up to his reputation of being a deep sleeper, gentle snores and snuffles coming from underneath his mop of hair. John reached out and tucked an escaping curl behind Sherlock's ear. He trailed his finger down to a freckle on Sherlock's neck and then, spotting another nearby, let his fingertip move gently across the skin. His finger continued down, swirling around each mark. Once he got to Sherlock's lower back, the man in question stirred.
"Do you mind?" He mumbled, voice gravelly with sleep.
"Not at all," John smiled, as he continued to connect Sherlock's freckles.
An eye peeked out from under Sherlock's fringe, "what are you doing?"
John smirked, "playing dot to dot. Hold still."
The eye rolled upwards and then disappeared back under the hair as Sherlock shuffled back into his pillow and moved a leg to hook over one of John's, "keep doing that. It feels… nice."
Grinning, John pushed the duvet away down to the foot of the bed, and started his finger trail again. When he reaches a sensitive area, Sherlock squirmes and John stores the information in his mind for future use. When he gets to where he had previously been interrupted, he finds that not only was Sherlock's back freckled; they littered his hips and thighs.
Once satisfied he'd found them all, John laid out half on top of Sherlock and curled his fingers into unruly locks.
"Feel better now you've done that?" Sherlock said into his pillow.
"Much," John smiled and kissed Sherlock's ear, "they're beautiful, you know. You suit them."
Sherlock grunted, "you should see Mycroft's in the summer. He gets patches of them everywhere."
John laughed and nudged Sherlock's lips up for a proper good morning kiss.