Chi-Ho (Kim Woo-Bin), Dong-Woo (Lee Joon-Ho) and Gyung-Jae (Kang Ha-Neul) have been best friends since high school. Now, they are all 20-year-olds. Chi-Ho has a girlfriend, So-Min (Jung So-Min), but he only thinks about wooing other women. An accident leads Chi-Ho to spend time with aspiring actress Eun-Hye (Jung Joo-Yeon). Dong-Woo hopes to work as a comic artist, but his family’s poor financial situation has Dong-Woo juggling several part-time jobs. So-Hee (Lee Yoo-Bi) is the younger sister of Gyung-Jae and she just adores Dong-Woo. Gyung-Jae is a freshman in college. He hopes to land a job with a large corporation. Gyung-Jae then meets an upperclassman, Jin-Joo (Min Hyo-Rin), who takes an interest in him and he falls in love with.
治浩、京載、東宇三個剛剛步入20歲的高中同窗好友，治浩（金宇彬 飾）是個整日無所事事的花花公子，只會把妹，直遇到了「她」；三人中最聰明的京載（姜河那 飾），內向害羞只會讀書，在心儀的對象前，總是沉醉於妄想而無法傳達心意；夢想成為漫畫家的東宇（俊昊 飾）家裡破產，生活只剩下永無止盡的打工。三個好友在成為真正的大人之前，擁有無限美好的二十歲，卻老是出包，糾在一起卻成」糗」在一起！充滿無限可能，可以勇敢去愛，夢想該瘋狂去追的二十歲，三人該如何擺脫衰小魯蛇命，碰撞出如何燦爛的愛情、友情火花呢?