Young-ho doesn't have any dreams for his life. He has been studying for three years to enter a university. He decides to send a letter to his childhood friend So-yeon. But her younger sister So-hee receives the letter instead of her sick sister. So-hee writes back to Young-ho, pretending to be So-yeon. Meanwhile, So-hee takes care of her sick sister and also runs a secondhand bookstore with her mother.

Always wearing a smiley face, Oh Ji-ah exerts herself no matter what, dreaming of a bright and shining future. But then, she is diagnosed with thymus cancer out of the blue. In spite of that, the company and her family force her hand as usual… While she is living her usual life, her friend Anna comes to see her. Anna, Jia’s role-model as the CEO of a company, suggests going on a tour around the country in a convertible the very next day but Jia refuses to go due to the pile of work she has to do and her upcoming surgery. And the day after, Jia faces the mourning portrait of Anna. Suffering from burn-out, Jia buys a ‘Cabriolet’ convertible with the money she saved up for surgery and takes off on a tour around the country.

It relates a time-slip story which takes Jung Yak Yong, known as Dasan, one of the greatest thinkers in the later Joseon period, from the past in 1818 to the present in 2022, as he becomes elected as the 20th president of the Republic of Korea. Jung Yak Yong was a Korean agronomist, philosopher, and poet. During his time, he wrote highly influential books about philosophy, science and theories of government and held significant administrative positions.