Her skirt was torn off at the back, which she didn't notice.

(Chapter originally by Phantom Pen on writing.com)

Toriumi thought she heard something as she stood up, but quickly wrote it off as one of her students putting something away. Had she been more curious, she would have noticed that the back of her skirt didn't leave the chair with her. Instead, she simply held up the stack of surprise quizzes for the whole class to see, and was met with a chorus of groans.

"Yes, I know, it's terrible. If you did the required reading for today, you shouldn't have anything to be afraid of." Toriumi said, walking up and down the aisles of desks as she distributed the quizzes.

Little did Toriumi know that doing this gave every student in class a clear view of her panty-clad buttocks. That would have been bad enough on its own, but Toriumi's choice of underwear for the day was... less than professional. Rather than a simple solid color, her panties were decorated with little red hearts, eliciting several snickers from more than a few students.

Toriumi, meanwhile, figured the snickering was caused by some class clown fooling around. Technically true, but not for the reasons she suspected. As the last of the quizzes were handed out, Toriumi returned to her desk, still oblivious to the fact that she'd just shown off her underwear to her entire classroom. Things were about to get worse for the teacher as she returned to her seat, when-