Mist of the Realms

If delinquents were being shaped during middle school, those delinquents were fully developed during high school—too excited to be adults yet could not handle pain. That was why many tend to keep to themselves just to not ruin their high school lives.
Yujin had always known that her classmates were delinquents of some sort so she stayed away from them—especially from those three guys who were occupying the seats at the back. They were perfect—too perfect that it annoyed her and thought that they were weird.
Still, she was so surprised when she saw them ganging up on some old men who suddenly became a shadow-like huge creatures. She witnessed how her classmates swiftly fought with the creatures in a nonhuman-like manner.
Yet she did not faint when that happened, no, but she did faint when the said creature held her as a captive and it suddenly decayed.