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.
Kang Ha-neul
Chun Woo-hee
Kang So-ra
Lee Sul
Lim Ju-hwan
Lee Hang-na
Lee Yang-hee
Park Se-hyun
Kim Sung-kyun
Ko Gun-han
Nam Hyun-woo
Kim Min-seo
Kang Young-suk
Choi Myeong-been
Won Ji-u
Go Woo-rim
Lee Tae-young