Tim's heart started to beat faster as he found he was able to service less and less of his own manhood. The monster was already 30 inches and gaining ground fast. Tim felt pressure building up throughout his body, and started to panic.
It was true, he had been a little disappointed in his own little 4-inch miracle worker, but it had never let him down. 8 inches seemed a respectable size for a man. 12 or 15 inches was freak-show quality. Here he was, with more than twice that standing hot against his chest. He fell backwards onto the floor of the tub, no longer able to keep his balance as his center of gravity shifted. Huge watermellon-sized testicles pushed his knees to the side.
As the tip of the giant rod pushed past the top of his head, he knew he had to do something. He squeezed it against his chest and started licking the sensitive head, saying, "Down boy," and "That's big enough for one day," and "How about a little smaller now?"
It wasn't clear if his efforts were having any effect on the growth of his sex, but all the attention did bring his orgasm to the fore. He felt his balls contracting, and as they tightened, he could feel every muscle in his body tightening up too. As his entire form bunched up for its first spasm, it was all Tim could do to hiss the command "Shrink!".
With the first contraction, and every subsequent wave of pleasure, shrink it did. As each wad of cum sped down the long hose which was his dick, the hose shrank around it, squeezing it even harder. The result was that each bucket of cum was hurled out of Tim's body with incredible force, splattering in every direction.
Tim would never have believed that having your cock and balls shrink could feel so good. Of course, the fact that his sex weighed more than the rest of his body when the orgasm started probably had something to do with the buzzing in his head.
Tim shrank much quicker than he had grown, and as his orgasm started to peter out, he was able to take his erection in both hand. It slid down to "only" 12 inches in his grasp, and finally spent, began to soften. His senses finally returning to their normal order, Tim surveyed the mess.