Taesan, a young team leader at Jang Hyun General Construction, reunites with his first love from college, Suyeon, in Jochiwon, where he arrived to prevent a flood at Heungbok Reservoir . "You're still the same, Lee Suyeon. Thoughtful, cautious, and indifferent..." Taesan feels the same emotions for Suyeon, who refuses to waver. If anything, it's that they've grown as much as the 10 years we've spent apart. "Hesitate and think long and hard. I'll wait." I crossed the invisible line before you a long time ago.