“You must never let anyone find out that you’re a girl! If you do, the entire world will be after you.” Due to a strange biological catastrophe that affected the X-chromosome, there are no girls being born in the world! The only girl left unaffected by this is Kang Ho Soo, who woke up 30 years later from a preserved sleep to find the world filled with men! Now she must hide her identity as a female not just from the whole world but also from the school's biggest troublemaker Park Yoo Ah who also happens to be her roommate! Will she be able to survive the school year?!