She gets turned on while fixing her panties.

After taking a breath, she looks around to check for people. The bus isn't terribly full, especially not near the back. So, Kim takes this opportunity to check on her situation below. Lifting up her skirt, she notices that the panties are starting to ride up in the front as well. Hints of her shaven lips are peaking from either side of the fabric. Blushing, Kim hastily tries to pull the fabric out from the front. As a result, the fabric in the back starts digging in more, causing her to unexpectedly moan in surprise. "Ohh!" Coming to her senses, she looks around franticly, embarrassed by the noise she just made. Thankfully, no one seemed to have noticed. Getting back to her panties, she carefully stretches the sides of the front part of the fabric to hide her lips. She then lifts herself from her seat a bit and reaches behind to fix the digging they're doing into her small, cute butt. However, everytime she tries to pull it out, the front starts getting pulled into her again. Each time, Kim trying to suppress the idea that this might possibly feel good to her. Eventually, she comes to the conclusion that the back will just have to stay in her butt, no matter how uncomfortable it might be. Better to have a thong in the back than a pull in the front rubbing against her clit. As she adjusted her front again though, her fingers glide over her pussy. Weirdly enough, she feels the urge to satisfy herself. This thought barely enters her mind before her fingers start slowly rubbing along her slit through the panties. Her thoughts get lost as she strokes herself, enjoying the alone time she's having in the back of the bus. She continues rubbing herself, her mind focusing on the tightness the panties are giving her in her ass. Gradually, and without realizing it, she begins tugging on the front of her panties, letting them slide between her lips. As the pressure increases on her clit, her pussy becomes more and more wet. She starts noticing how easily the panties are starting to slide through her with the dampness of her juices lubing up the fabric. As she pulls on her underwear more and more, she becomes more and more turned on. Her other finger slides into her slit as her other hand continues pulling. Suddenly, as she's starting to lose her focus in her hormones, the bus stops suddenly, snapping her out of her trance. Her face turns red at the realization at what she was just doing. Quickly flattening her skirt in the front, she grabs her bag and stands up. Being in the back of the bus, she was going to be the last one off thankfully. She still couldn't wrap her head around the situation she just put herself in. Masturbating on a bus with strangers, possibly other students, within feet of her. Shaking the thought from her mind, she walks down the isle.