John considers relenting, or at least shifting his focus to something a little less intense in the interest of drawing things out. But Martin begs him, breathless, not to stop, and he doesn't have it in him to deny so desperate a plea. He hums his assent against and around him, circling him again with his tongue, cheeks hollowing as he sucks a bit harder. His left hand settles into a steady rhythm of pinches and tugs. Then — in the interest of getting in at least one more impulsive little experiment before the end — John risks... not quite a nip, but a light, playful scrape of his teeth against the soft skin just to the side of Martin's areola.