"Uh...transform!" Cassie blurted out.
"Oh good, I was hoping you'd say that. Ok, for your transformation, you're going to start shrinking slowly, say, an inch a minute, and the smaller you get, the more aroused you get."
Cassie's eyes widened as she felt a shiver run up her spine. Before she could say anything, Rachel's thumbs began to rub against her nipples and her friend kissed her.
Sure enough, Cassie slowly began to dwindle in size even as her need increased. Rachel found that she enjoyed her newfound dominance over her friend immensely. She pushed her friend down, and slid Cassie's skirt and panties off of her shrinking form, and ran her hands along the smaller girl's hips. She was rewarded with soft mewling noises of pleasure, much to her excitement.
Rachel then leaned over her friend and kissed her tummy, her tongue making little circles around Cassie's belly button. The shrinking girl writhed, clearly enjoying the attention.
Cassie was no bigger than a fifth-grader by this point, and Rachel pushed apart her legs as she leaned in. She'd never licked another girl's pussy before, and she couldn't resist the urge.
Cassie's scent was strong, yet not unpleasant, and the tiny girl moaned again as Rachel penetrated her with her tongue. Rachel found she enjoyed her friend's taste, and she used two fingers to open Cassie further. She pushed her tongue in deeper, and Cassie's back arched.
Rachel could feel her friend's pussy getting smaller, tighter around her tongue. By now, Cassie was no bigger than a third-grader, and she continued to shrink. Rachel lifted the small girl and placed her on the bed, marveling at how light she was.
Finally, Cassie's moans reached a fever pitch, and Rachel could feel her friend's body stiffen with release. Her tiny pussy was suddenly very wet, and Rachel eagerly lapped up her friend's juices.
Finally she backed away. Cassie had dozed off, her arms stretched out wide. She was well under 4' tall by now, which made her look as precious as a doll. Climbing up onto the bed, Rachel pulled her friend into her arms and pulled the blankets up around them to get some rest.