This show is based on the novel "Why Secretary Kim" by Jung Kyung-Yoon (first published April 3, 2013 by Gaha).
Lee Tae Hwan, who was born in 1995, will be playing the role of 35-year-old Lee Sung Yeon. Lee Sung Yeon is the older brother of Park Seo Joon's character Lee Young Joon, and Park Seo Joon was born in 1988.
In episode 2, there's a photo of Lee Young-joon meeting Barack Obama and Angela Merkel in 2009.
This show marks Park Min Young's first time playing the leading role in a romantic comedy television series.
Lee Young-joon (Park Seo-joon) lives in the same place in Why as Kim Joo-won (Hyun Bin) In Secret Garden.