“I realised it then… That this summer would be the hottest one yet.” Why are we lonely when there are so many people everywhere? A question that seems destined to be asked today, when relationships are volatile and come and go with ease. Jae-hee and Seung-woo don't have the answer either, and turn to their dating apps for some semblance of comfort. But a simple tap of the phone screen will turn into an uncontrollable longing for one another when a single message pops up on the screen: “Hello, Stranger.”