Jason watched the mare carefully over the next few minutes and then, to his utter delight... he saw her come back. Just a little. The sparkle of intelligence in her eyes had returned, though dim it was.
“S-Sweetheart?” Jason asked gently.
The mare glanced up at him, licking her lips, and gave him an alarmed look. Less desperate. More urgent.
“More?” He whispered.
The mare whinnied out loud, watching Jason closely with wide eyes, and turned to present herself, lifting her tail to allow him access to her pussy.
With a look of determination, Jason stepped back onto the stool and drank deeply of her scent, leaning in and kissing her pussy lips to spread the aroma over his face. That did the trick. He was hard again in moments.
He slipped in, grabbed the mare’s flank in his hands, and went to work. The second orgasm took longer, having staved off her total loss of self, and as he shot his load inside of her he felt a deep satisfaction as he realized the prolonged contact with her pussy juice had grown him.
Panting, he slipped his cock out and marvelled as a stiff eight inch length emerged. His sheath was back, and he was starting to darken up to equine coloration across his shaft again.
“There.” Jason said in relief, almost teary eyed. “I’m getting horse sized again, sweets.”
The mare turned, much more aware now, and nodded at his transforming erection. As the latest injection of cum began to take effect, the horse’s sexual excitement returned, and she let out a whinny of encouragement.
“Keep going?” Jason panted.
The mare nodded sharply, wagging her butt.
“I’ll do my best. I don’t have a lot left.”
She snorted and adjusted her hind legs. He was still rock hard and starting to soften. Jason slipped back in to her now hot and wet pussy and felt an intense pleasure as he felt himself growing. The stronger her juices... the stronger his response.
As his dick began to really enlarge and reshape again, Jason felt a flood of arousal. He humped with careless abandon, exposing himself to her pussy juice as long as he could. With each stroke his cock felt bigger and heavier, and panting he withdrew long enough to get a glimpse as his dick. It had regrown to a thick horse shape and now sat just beneath a foot long. Almost back to its 14 inch largest.
He slipped back in, making the mare jump, and he continued to fuck her. He felt his balls tingling sharply and whimpered as he felt them growing larger. Their dangling orbs began to reinflate, presumably darkening as well, and he gasped as he felt a rush of... filling? He had regenerated his cum. That excited him even more, as if the process itself was urging him to fix her.
He felt a jolt as he reached the size he had been the night before... a nice thick 14” long horse cock pulsating inside the mare. He felt his balls big and heavy again and the trail of his thickened horse flesh swelling up his butt crack.
He kept fucking, and drenched with sweat and surrounded by the warm comfort of the mare’s aroused scent, it didn’t take much more to urge him to cum again. He felt his tip swell and a thick jet of cum spill forth into her.
As he drew away, trembling as he sat down on the stool watching his floppy horse dick start to shrink again, the mare let out a groan. She too, had gone back to the state before he left her the night before.
“I-I’m back.” The mare announced, her voice rich and womanly again. “Oh, thank God, I’m back!”
She turned to face Jason and offered a gentle lick to his receding cock. He jolted and gasped. It was... growing again. Slowly... but he was going to be even bigger in a few minutes.
“You almost lost me,” she said worriedly. “I was... gone. I had faded away.”
“I-I know,” Jason said, relieved. “But now you’re back to where we were.”
The mare glanced down at her front and back hooves, now splitting into their strange transformed state, and her eyes widened in fascination.
“No... I’m going farther this time. And... so are you.”