Just the tip.

John just can't resist. His hands shoot straight for her tits, mauling them more than groping them. She's still out cold, giving him the confidence to remove her bra. He took in the view of her perky tits capped with her soft pink nipples for all of half a second before he stretched the crotch of her panties aside and started rubbing his cock head up and down her wet slit. Although she remained silent John could see her skin starting to flush.

Then he put the tip in. Just the tip. It felt amazing, her warm wetness stretching and squeezing around his bulbous head. If just the tip felt this good than going all the way must be mind blowing. But could he really do that?