The older sister who mistakenly entered the AV corner of the video store. She's so absorbed in searching that her panties are showing. It's impossible not to get an erection for such an erotic body meeting in such a place. In the cramped store, her buttocks are tightly pressed against the hard penis, making them squirm. Both of their excitement is evident. It's okay to do it right there so as not to be noticed by the staff or other customers.