What happens when Kim Junmyeon, a well-trained bodyguard suddenly signs up to become a nanny?  Wu Sehun and Wu Jongin, or the Wu's Siblings, turned his life upside down and things got more complicated when he found himself falling for the siblings' father, Wu Yifan.     

In which, Jongin suddenly questioned why her boyfriend chose her as a girlfriend and she started to feel insecure about their relationship. It all started when she noticed that her boyfriend had a new hobby, which was staring at almost all of the popular girls in their college.