The plot centers around the relationship of a 15-year-old couple, Jenny (Park Min-ji) and Juno (Kim Hye-sung), who meet in school. Jenny is a smart, bright and pretty girl. While Juno is cute, cool and good at sports and just got transferred from another school. When Jenny discovers that she is pregnant, she and Juno decide against having an abortion, opting for parenthood instead. Juno starts delivering newspapers to earn additional money to buy the food that Jenny desires.
Juno strives to carry out the duties of a good father, and always stays at Jenny's side, taking care of Jenny's nutrition for the sake of their baby. Jenny becomes jealous due to her condition and gets into a mishap with Pyoy, a girl trying to flirt with Juno. Juno breaks up the fight and asks Jenny to never do that again because of worry for their baby.
They even went to places for pregnant women, practicing an exercise for pregnant mothers and spend their time together at school and outside. They go out one day a date and take a boat out on a lake, but the ropes that bound the boat were lost and they are left stranded. They try to seek help but there is no mobile phone connection. They wait there until midnight when a fisherman arrives and sends both of them back home. Jenny gets scolded by her mother for returning late. They try to conceal the pregnancy from their families for as long as possible, but the truth is revealed eventually when Jenny's middle sister finds out about her pregnancy. Jenny and Juno tell their parents about her pregnancy, but they do not approve.