'You can count on me, Mr. and Mrs. Jung. I will try my best to keep an eye on her' Yunho said

'Thank you so much, Yunho.' Hyori said

Jessica, who is a troublemaker got her parents, Rain and Hyori really worry about her so they hired Jung Yunho, a 17 years old to take care of Jessica. They register Yunho into the same school as Jessica. Yunho promise himself that he will change Jessica and leave after. But what happen if he start to fall for her each day.