Tae-san, a young team leader at Janghyeon Construction, arrives in Jochiwon to prevent flooding from the Heungbok Reservoir — only to unexpectedly reunite with his first love from college, Su-yeon. “She’s still the same, Lee Su-yeon… thoughtful, cautious, detached.” As Tae-san feels his old emotions stirring, Su-yeon tries to stay steady. The only thing that has changed is the decade that has passed without each other — the time that turned them into adults. “Take your time to hesitate and think it through. I’ll wait for you.” Because the invisible line that once stood between us… I crossed it long ago.