Sister Mary had Jim sit on the side of the bed, the sheet draped across his lap for modesty. "What are you going to do?" Jim asked worriedly. Mary simply smiled and leaned in close. Before Jim could react, one of her arms snaked around Jim's neck and drew him into a deep kiss. With eyes wide, Jim sat stunned, while the nun began to massage his tongue with her own. His pulse thundered as the kiss continued, and just as he thought he would pass out from the sensations, Sister Mary broke the kiss. Looking down at Jim's hard on, she smiled.
"We have waited a long time for this. I am glad your body is so responsive." Reaching under the sheet, Mary began to stroke Jim's shaft. His cock was straining against the skin, as if her touch was willing it to grow further. She began to kiss his chest, and through the haze of pleasure, Jim asked again,
"What are you doing?"
As she moved her lips from place to place on his body, Mary responded, "I am bringing about your full potential. The Church is afraid of you, but there are those of us who have been watching, waiting for someone like you to appear and remake the world in your image."
"Someone like me? My image? What are you talking about?" Jim could feel his chest growing tighter. His arms thickened as his soft teenage body began to ripple with muscle. He wasn't certain, but Jim thought Mary's hand felt a little smaller around his shaft as well.
"We have sent hundreds of men into that cave over the years, looking for one who might bring the return of the Corrupter. His power always overwhelmed their frail sould and bodies, converting them into more of his essence, that black liquid which you alone have managed to resist." She began to move down his body, tracing lazy circles around his navel with her tongue. "Your soul is strong enough to survive the change, if we can just make it suitible for our master." With that, the fallen nun pulled back Jim's sheet. Jim watched in mute fascination as she licked his shaft from base to tip. Before his eyes, his cock grew another two inches, growing thicker as well. With a lusty moan, Sister Mary plunged Jim's member into her mouth, taking his entire length down her throat.
Jim couldn't control himself. His powerful arms gripped Mary's head while he thrust his growing shaft in and out of her mouth. As her throat grew tighter and tighter, Jim threw his head back in a bestial roar. He began pumping his seed into Mary, who greedily swallowed all she could. As he came, his eye became bloodshot. His fingernails grew long and sharp, darkening to a glistening black. With a slight pop, Mary pulled Jim's swollen member out of her distended mouth. Rising before him, she pulled up the hem of her habit. Her slit was lightly dusted with pale blonde hair. "Oh, God," Jim gasped past lengthening fangs, "I can't...I want to..." Sister Mary pulled his head to her sex, rubbing her slit across his face and smearing it with her cum. Jim's eyes began to glow red as he buried his tongue into her.
Sister Mary howled as she came. Even though Jim had not fully manifested as a demon, she could already feel his power. Reaching up under her habit, she fondled her breasts. She could feel them swelling, and her bra was becoming uncomfortable. Unfastening the garment, she freed her breasts, teasing her nipples briefly before raising one to her mouth and sucking on the soft flesh. As she came again, Mary could feel a shift in Jim's body. The changes he was experiencing were coming to a head.