Initially, an audition was held to cast the female lead, and a friend of Kim Ji-hyun's brother heard about it.

[4][5] Ryu Soo-young, the film's male lead, was also a first-time movie actor, though he had experience appearing in TV dramas.

He chose to star in Summertime because his manager was close with the film's producer, and at the time staff needed more male actors.

Ryu was also reluctant to appear in the film, but he accepted after the director urged him it was not just "people taking off their clothes".

[9] According to Ryu Soo-young in a 2012 episode of Radio Star, the movie's script was substantially cut to fit its run time.