Jeong Eunji is a high school music teacher. She has a colleague and also a long time friend named Lee Howon, a dance teacher and whom she secretly has feelings for so long but he is engaged with her other colleague who also teach music, Park Chorong. On winter break, Eunji has volunteered in an orphanage in which she met Kim Sungkyu, the son of the founder of the orphanage and who is forced to help. What would be their roles in each other's life? Let's find out in this story! 

Story of a girl and a boy who made a lot of mistakes. And of the biggest mistake they've done is when they meet each other one night, and did the very sacred and most important thing for two people who love each other. Yes, they did that 'thing', the girl got pregnant and there.... their story begins.