Music producer and composer Ha Rib made a contract with the devil to trade his soul for fame. This devilish transaction brought him all the fame he could ask for, producing many hit songs. As the contract expiration draws near, he bargains with the devil for an extension. For that, he must find another person to sell the soul. Ha Rib finds a perfect candidate, but contemplates because she would have to suffer for 10 years for his selfish fame.
Cellphone app Joalarm is created. If someone likes you and they are within 10 meters of you, the alarm for the app rings. The app also shows how many people like you, but the app doesn't reveal specific details on who likes you.
Kim Jo-Jo (Kim So-Hyun) is a high school student. She is pretty and smart. She seems like cheerful person, but her parents died when she was young. Since the death of her parents, Kim Jo-Jo has lived with aunt's family. Living there is not easy for Kim Jo-Jo. She doesn't download the app Joalarm.
Meanwhile, Hwang Sun-O is a popular male student at the same high school where Kim Jo-Jo attends. He is the son of a wealthy family, but he is not loved by his parents. His best friend Lee Hye-Young also attends the same high school. Hwang Sun-O notices that his best friend Lee Hye-Young likes Kim Jo-Jo. Hwang Sun-O wants to know if his friend really likes her, so he kisses her.
Wie Dae-Han (Song Seung-Heon) is an ex-lawmaker and is a materialistic kind of politician. He wants to get elected as lawmaker again. One day, 18-year-old girl Da-Jung (Roh Jeong-Eui) comes to him. She tells him that he is her real father. Her mother raised four children, including Da-Jung, alone, but she died in a hit-and-run accident. Da-Jung is the only one now taking care of her 3 younger siblings. Wie Dae-Han accepts Da-Jung and her 3 younger siblings. He carries out “The Great Show” to become a lawmaker again.
“We are neither kids nor adults. When do we become adults then?” Min Jae and Seo Yeon are no different from ordinary 17-year-old high school students. Min Jae is silent and sensitive, yet a good student. Seo Yeon who plays the piano wished to enter an arts high school but failed. As they grow into adults, their surroundings and the reality they face get harsher. These two somehow similar but different friends get closer as they overcome their growing pains together.