Park Yeomin is an University Student who really hope to pass X class well which is teached by a strict professor. But, luckily, her prof. has an project, so, he can't teach Yeomin anymore. His assistant comes to Yeomin class and brings the news that he'll exchange prof. with him. Before that, Yeomin has a little accident with him and now, Yeomin score is in that assistant's hand.