'X101' is the biggest ruthless mafia gang in South Korea that can basically kill you big time. At the top of the underground, people would be even afraid to mess with them. They get whatever they want and no one can stop them.
Meanwhile Hangyul, Jinhyuk, Yohan and Junho are your average students at university preparing for exams with innocent funny friends. It all starts going wrong when they get invited to a party at one of the biggest luxury clubs in Seoul and get pulled into the harsh mafia world. What's worst is they start falling in love with the dangerous mafias from 'X101'. What could possibly go right?