After you finish pissing, you turn back to the man. He shouts in surprise as you grab his shoulders and push him against the toilet wall. You turn him round and rip his jeans and underwear off. He whimpers, "Please don't..." as you unsheath your raging erection. You both moan loudly as you push your foot-long cock into his tight asshole, pressing your tip into his prostate. You grind your hips back and forth, your pre making a squelching sound as you continue to thrust. He shouts as he sprays his cum onto the wall, but you continue to thrust. After one final push into his anus, you unload what must be litres of cum into him, continuing to pump as your orca semen pours out.
As you thrust, you notice the skin around his anus is different. It is the same black colour and wetsuit-like texture as your skin, and is continuing to spread. His ass seems to plump up and tighten slightly, and a nub starts to poke out above his asshole. You orgasm again, pumping more semen into his dripping anus, and speeding up the changes. The new skin spreads down his legs, causing his thighs and calves to expand with muscle. In his pleasure, the man hasn't seemed to have noticed the changes, even as his small erect penis lengthens and thickens into a similar size to yours. You are forced to pull out as the nub suddenly pushes out and swells into a full-sized orca tail. Looking behind him to see why you pulled out, he screams as he finally realises what is happening to him. He shouts at you, What the fuck did you do to me!" but is silenced as you take his now huge cock into your mouth, causing him to moan in pleasure. His new skin moves up his body, tightening his abs into a perfect six-pack to match his muscular legs. You continue sucking, almost choking as his chest swells to become huge, smooth, heavy pecs, even more muscular than yours! He flexes and grins as his biceps pump up, and sprays his first orca cum down your throat, in turn causing your muscles and genitals to slightly grow. His hair falls out as his skull cracks into the correct shape for his form, and his attractive face reshape to fit his new orca-man body. He stands up, allowing you to take in his body, which is strong and muscular, but more lean than your bulky form. You rub your hands down his lycra-like skin, enjoying the feeling of the smooth material wrapped around his bulging muscles. Judging from the seams down his sides that you also have, he is still a costume like you. You smirk at each other, and both sneak a glance at the bulges behind your sheaths.