Helmed by director Lee Eung-bok, the man behind Descendants of The Sun (DOTS), Guardian: The Lonely and Great God; and writer Kim Eun-hee (who also wrote the zombie series Kingdom), Jirisan is a show that revolves around the story of mountain rangers who want to save people in Jiri Mountain National Park.
Seo Yi-gang (portrayed by Jun Ji-hyun / Gianna Jun) is the best ranger at Jiri Mountain National Park. She knows everything about the area, including how to climb the mountain. Kang Hyun-jo (portrayed by Jun Ji-hoon) is a rookie ranger at Jiri Mountain National Park. He graduated from the military academy and was once an army captain. He has a secret that he can't tell anyone. These two people become partners and they work to save people around Jiri Mountain National Park.
The production team shared that the female lead character Seo Yi-gang was envisioned as a “healthy and beautiful female warrior”. The first - and only - actress they wanted for the role was Jun Ji-hyun.
Meanwhile, for Kang Hyun-jo's role, actor Ji-hoon's smile was what won the production team over. “He is able to express innocence, playfulness, cruelty, strength and much more with just his smile. He matches our vision of Kang Hyun-jo who is warm, can exert an air of dominance, and is able to express despair.” Discussing Jun and Ju’s on-screen chemistry, the production team shared, “In previously released trailers, we can see that Gianna Jun is in good form as the senior park ranger. Although the shooting process has been extremely physically demanding, Jun has kept the on-set atmosphere and chemistry going strong.”