Zack begins unravelling her shirt

Zack slowly reached out and took the thread in his fingers. Then he pulled it back and carefully slipped his arms under his desk. Keeping the fabric out of sight from everyone else, he began slowly tugging on the thread. Much to his delight, it offered little resistance and he soon settled into a rhythm of unravelling Mackenzie's shirt from behind. Mackenzie, meanwhile, was dutifully focusing on her midterm, and was none the wiser.

At first he wasn't sure if he was making any progress. But after a few minutes, Zack noticed the bottom of Mackenzie's shirt had risen by half an inch or so. His midterm completely forgotten, a grinning Zack continued his covert efforts and the oblivious Mackenzie's shirt continued to unravel.

About half an hour later, Zack had rendered Mackenzie's shirt short enough that it no longer covered her bra clasp in the back. The eager boy had paused his efforts as he contemplated a new decision before him. He mulled it over for another minute before his mind was made up. Zack reached forward and quickly unhooked Mackenzie's bra. Then he moved his hands back under the desk and immediately went back to work unravelling the shirt even further.

Mackenzie paused mid-question as she tried to figure out what she had just felt. It had felt like something lightly touched her back, but she wasn't sure what it could be. That was, until a moment later when Mackenzie unmistakably felt her bra stop supporting her breasts. Her eyes went wide in surprise and the redhead tried to subtly glance down at herself. To her even greater surprise, she saw that her shirt was even shorter now. It didn't even cover the bottom of her bra anymore!

Mackenzie didn't want to get accused of cheating, but she had to know what the hell was happening. She chanced a glance behind her, only to noticed a thread leading away from her shirt and under the desk of a grinning boy behind her. The asshole behind her was unravelling her shirt!

Mackenzie reached back and managed to snap the thread, cutting off Zack's access to her ever shrinking shirt. Then she leaned as far forward in her seat as she could, hoping Zack would no longer be able to reach her bra or shirt. Safely out of reach, Mackenzie tried to forget about the jerk and refocus on her midterm.