Kim Myungsoo, a leading industrialist in Korea. He is a hot young single father who is on his 22 years old already become a CEO of Kim Corporation, the largest company in South Korea. Handsome, workaholic, loyal and cool. What a perfect guy that every woman is begged for to be their husband.  But he is lonely because he has lost everyone who is dear to him. Due to distraction, he mistakenly kills a husband and wife in a car accident. Only their son was alive. The judge then sentences him to look after that child, and to do so without ill-treating him. Myungsoo gave that child his family name.

Kim Myungchan, 5 years old. A little trouble maker, he is smarter than the child in his age. Because of the accident, he was traumatized and amnesia. All he knew is Myungsoo is his father. Even Myungsoo didn't really treating him like his own son but he didn't refuse him when he call him Daddy. Myungchan often asked him about his mother but all that he got was an ignorance from Myungsoo. His relationship with Myungsoo doesn't going well. Myungsoo was cold with him. Myungsoo was too busy to give Myungchan attention. Lack of love and affection, Myungchan growth to be a naughty and uncontrolable in his school. Bad behavior and cold attitude, little Myungchan is really a copycat of Myungsoo. Even his teacher is give up with him.

Lee Sungyeol is a new teacher in Myungchan's school. A tall charming guy with gummy smiles and cheerful   attitude. He is an orphan child. That's why he wanted to be a kindergarten teacher. He want to share his love which he never got and dedicated his life to the children.

What will happen with them? Will Myungsoo accept Myungchan wholehearted or throw him away after his duty ends? What will Hyuna do to get rid of Myungchan and marry Myungsoo? Will Myungchan get his happiness and turn to be a good boy? What will Sungyeol do to him to turn Myungchan into a good boy again? Will Myungchan open up with Sungyeol or he would ends up being bullied by Myungchan? And what will happen with Myungsoo when he meets Sungyeol? Will Sungyeol able to bring Myungsoo and Myungchan together as a real family?