35-year-old architect Seung-min (Uhm Tae-woong) receives a visit at his office from a woman. Seung-min doesn't recognize the woman at first, but then realizes the woman is Seo-yeon (Han Ga-in). Seo-yeon is his first love, but he hasn't seen her since his freshman year in college. Seo-yeon now has a request. She wants to hire Seung-min to rebuild her home on Jeju Island. 15 years ago, Seung-min (Lee Je-hoon) is a naive young man beginning his architecture studies in college. He first meets Seo-yeon (Bae Suzy) in his Architecture 101 class. As they work on a class project together, Seung-min and Seo-yeon begin to fall in love. Back to the present day, Seung-min is hesitant to take Seo-yeon's job offer. Seo-yeon persists and even goes to his boss with her wish. Seung-min now has no choice, but to take on Seo-yeon's home project. Old memories of love and heartbreak will soon resurface, as they find themselves at different junctions in their lives...