Jenny, Juno centers on the title characters of Jenny and Juno, two fifteen year old middle school students whose one night of romance has dramatic consequences for both their lives. After careful deliberation, the two expectant parents decide to keep the baby.
After being dumped by her boyfriend just before their 100-day anniversary, Ha-young meets a college guy named Hyung-joon when she kicks a can that accidentally hits him in the face and causes him to scratch his Lexus. He demands she pay him $3000 on the spot.
Eunjin who is a living legend among the gangsters dominates the male-centered underworld wielding only a pair of her trademark blades. One day, Eun-jin finds her sister from whom she was separated at an orphanage during childhood, and her sister tells Eun-jin that her last dying wish is to see that Eun-jin gets married.
A novelist has an affair with two women, finding fulfillment in neither; a married businessman strays from his wife he can't satisfy; a naive young woman surrenders her dignity for her lover; and a married woman tries to find solace in a frustrating affair.
A young male model twists and manipulates people around him in his unending quest for money and pleasure. He is convinced that he is untouchable and can bend anyone to his will, so not even murder is an obstacle to his ambitions.
Yi-su, a 37 year-old professor, can't forget her first love Joon-ho who's missing in action in Vietnam. She meets Hyun-woo one day, who look surprising like Joon-ho. Hyun-woo investigates Yi-su who lives in the past and discovers that her pain stems from the Vietnam war. Hyun-woo can't help falling in love with her even though he's a student. On a trip to Busan, he confesses his love for her. But he soon realizes that the only man for her is Joon-ho. Min-cheol who fought along with Joon-ho sells his belongings to Yi-su at a high price. He tells her that Joon-ho died in a fire and they argue aggressively. Min-cheol commits suicide afterwards and Yi-su is also found dead in the campus pool.
After coincidentally witnessing a boy jumping from the rooftop due to pressures of the college entrance exam, our heroes conceive an idea for a learning device that works while you sleep. Dong-gi, Ho-tae, and Jae-ha go to Chairman Kim of an electronics company to get the funds to make it. They experiment the 'snooze machine' on their younger brother, Dong-seok. Once at the bottom of the class, Dong-seok goes to the top but he is ostracized by his classmates. They reject the snooze machine and shout, 'Let us live like human beings!' Ho-tae gets into an argument with the other two over the development of the snooze machine. He moves out but later is persuaded back by the great burst of laughter stemming from solid friendship. Arm in arm, the three face a brighter tomorrow together.
