BIG

人人都在追忆逝去的青春，希望重新回到十八岁的年纪，弥补当年的遗憾，完成未完成的事。可是对于现年三十岁的医生徐允在（孔侑 饰）而言，因为车祸而导致的灵魂互换，让他成了表面三十岁的大叔，内心却是十八岁的少年的事情，应该不是那么令人兴奋。 　　因为这次互换，徐允在实际上成为了高中生姜景俊（申原昊 饰），看着镜中陌生的脸，成为允在的景俊起初迫切想要找到回到真身的办法，可一时半会却找不到。于是景俊只得不安的开始了新生活，而他首先要面对的就是允在的未婚妻，也是自己老师的吉多兰（李珉廷 饰）。面对自己未婚夫性情的大变，让多兰很是不适应。而这还只是故事的开端……Gil Da-ran (Lee Min-jung), a high school teacher, is engaged to a handsome doctor, Seo Yoon-jae (Gong Yoo). Kang Kyung-joon (Shin Won-ho) a troubled transferred student from USA, one of Da-ran's students, got into a car accident with Yoon-jae. Kyung-joon woke up in Yoon-jae body while his own body stayed in coma. Da-ran and Kyung-joon (in Yoon-jae's body) had to pretend to be in relationship while working out how to switched back.