A slow careful seduction

You arrive at the beach and you carry the stuff to a perfect spot in the dunes. The wind is broken by the sand mounds around you, and the sun is perfect for an early spring day. You and Katherine setup the coolers, chairs and other stuff making a nice little camp for your day. You grab some sunscreen and coat yourself liberally, can't have a sun burn getting in the way of any close contact, and you try not to stare to much at Katherine as she does the same.

"Come on lets build a sand castle you say to her as you run down towards the water. You spend the rest of the morning with Katherine doing all the normal beach stuff, building sand castles, body surfing, walking along the beach look for interesting shells, all the while building your budding relationship with Katherine. The beach is almost empty as it is a weekday, and school is still in session. Soon it is lunch time and you suggest, "Come on let's grab some lunch, I'm starving."

Katherine agrees and the two of you wolf down the lunch she put together. After lunch you both decided to layout in the chairs you brought, catch some sun and let the lunch digest. You lie down on the chair next to her and watch as she undoes the back of her bikini top and lies down on her stomach, carefully holding the top against her tits. You watch the whole process hoping for a nipple slip or something, but soon she is settled in, her tits tight against the chair.

The sound of the surf, and the warm sun lulls you into a contented semi-slumber and you wonder if you are dreaming when you hear her say, "Put some more suntan lotion on me will you James?"

You would like nothing better than to put your hands on her perfect, hard body and you hop up grabbing the sun screen from the blanket. You squirt a little on her back; she jumps squealing, "its cold." You quickly start to smear the white cream across her brown back, feeling her firm muscles beneath the soft skin. You straddle the chair so you can get a better angle and your cock brushes against her tight ass as you reach forward to rub the lotion on her shoulders.

"Get down low on my back too, right at the line between my suit, and skin. I always burn there," she instructs.

You slip your fingers along the suit, almost rubbing her perfect ass, she moans slightly, "Oh, that feels good, my back is tight, go a little lower."

A little lower puts your hands right on her tight ass, but you don't object rubbing her firm cheeks a little. "Get my shoulders really well, I always burn up there," she tells you.
You lean up to get her shoulders again and you realize your cock is hard as rock. As you lean forward it touches her tight ass, and you can hear her gasp a little as you rub up against her. You can barely resist the urge to rub it against her ass more; you would like nothing better then to cum all over her tight ass.

Then Katherine says to you, "Is that what I think it is rubbing against my rear?"