Suddenly, Kayla began to thrust even harder, and faster into Alyssa's asshole. "God!..You're so fucking...tight!" Kayla whined as she relentlessly pummeled Alyssa's sphincter. Alyssa could only groan and moan as she was rammed into the barn floor. Somehow she didn't feel any pain, only a pleasant stretching sensation as a heat began to radiate from her anus. Unbeknownst to either of them, Alyssa was changing. Her asshole began to puff out and darken in color. Kayla began to pant and groan, her thrusts became erratic and her cock began to throb. "It's...coming!" Kayla huffed out. Alyssa didn't pay her any mind, she was lost in her own pleasure. Much to her surprise, she was beginning to deeply enjoy sex with Kayla. She could feel a pressure building in her cunt, she felt the best orgasm of her life building up. Kayla finally had enough and thrusted balls deep into Alyssa and came with a throaty wail, pumping tons of her seed into Alyssa's rectum. Alyssa's eyes opened wide upon feeling the virile blast inside of her and she came with a scream, her pussy erupted with a gush of girl-cum. A panting Kayla removed her cock from Alyssa's hole. She looked down to admire her handiwork and was surprised to see a horse's black donut where Alyssa's tight human pucker once was. The sight of her seed drooling from the hole made her softening cock throb and stand at attention again. "Again!?" Kayla groaned in frustration as her cock beat against her belly. Alyssa however was zoned out, lost in the heat in her ass. Slowly the haze faded and her mind returned, she felt sick. There was a bizarre heat throughout her entire body.