Twenty is the age that everyone considers to be the best time of their lives. However, we have never suffered from love for the opposite sex, dreams for the future, and passion for life as much as we did at that age.

The problems of 20-year-olds, which are childish and simple to the eyes of others, but are more serious than anything else to the people concerned. ‘Twenty Years Old’ look at the problems from their point of view and try to solve college life in a serious but pleasant way.

Two twenty year olds, Kim Hye Rim and Lee Ki Kwang, who attended the same middle school, meet again coincidentally after many years as a college student and an idol group member. Lee Ki Kwang is a member of popular idol group falls in love with Kim Hye Rim, his old friend from same middle school who has never dated before, as the two try to keep their love a secret from the rest of the world.

Due to an unplanned pregnancy, Ha No Ra married young and dropped out of school. But after two decades as a housewife, she finally gets the chance to experience college, alongside her 20-year-old son Kim Min Soo and his girlfriend Oh Hye Mi. Further complicating things, No Ra already has a strained student-teacher relationship, as her husband Kim Woo Chul and her first love Cha Hyun Suk wind up being her professors.

Born in 1981, So Won should be in her forties now, but when she became twenty in 2000, she encountered a witch by chance.

So Won was cursed by the witch because she turned down her favor. The curse was "to live as a twenty-year-old woman for the rest of her life." At first, she thinks it will be a blessing but soon starts suffering from the pain of losing her beloved ones and her life re-setting every year.

One day, So Won happens to spot the witch in a photo, so she heads to the resort in the photo's backdrop. To lift the curse, she sneaks in as a resort staff and meets Kang Hyun and Sang Wook there.

Hatachi no Koibito tells the story of Inoue Keisuke, a married salaryman. At the age of 50, he begins thinking about his purpose in life. By chance, he encounters Sawada Yuri, a 20-year-old graphic design student full of hopes and dreams for the future. Because of her resemblance to his girlfriend from long ago, he finds his heart unexpectedly beating faster... --Tokyograph