Jeff notices a white bit in the corner of his vision. Looking over, that's when he realized... he was a DIAPER? (There's no way she needs Diapers... right?) But despite his thoughts, he was indeed wrong; His sister wore diapers.
As he was sitting there, thinking about the situation, he heard some of his sister's thoughts; (I still don't understand how Jeff hasn't figured out about me needing diapers... I literally sat on his face in them!). Jeff, hearing that, felt disgusted, but at the same time... he wasn't sure how to think of it. On one hand, he was disgusted by having a diaper in his face once, but on the other, he was turned on by the thought of any girl being that close to him.
=========== Time skip; 10 minutes later ===========
Jeff was sitting there, listening in on his younger sister's thoughts. As he was listening though, he could hear sounds coming from inside of her; And with where he was located, he knew exactly what it was. He would have to watch his sister pee up close; A lot closer than he anticipated.
However, this is where he realized something; If he can hear Julie's thoughts, maybe he could warn her before she went? This is when he messed with his thoughts, so he can change his voice to avoid recognition.
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As he could hear her about to burst, he focused on her; Then, in a random voice, had told her that she needed to pee. He then listened in as she contemplated her options, before...