A dream of a vibrant college life. Go Yeon-seo meets Yeo Se-jin, a friend of a friend, through an introduction. The two develop a deeper friendship than the friend who initially connected them, and Yeon-seo gradually becomes a significant presence in Se-jin's heart. A youthful crush. The trials of first love. Thus, Yeon-seo endures the heartache of unrequited love for Se-jin for a long nine years. However, this was a feeling that must never be shown. Yeon-seo lacked the foolish courage to sever the bond of friendship built over a long time. She had to avoid it. Her feelings for Se-jin entirely. In the end, Yeon-seo even gives up her successful career as a powerful lawyer to cut off her feelings for Se-jin. Meanwhile, Se-jin feels an inexplicable anxiety due to Yeon-seo's sudden change and seemingly evasive behavior, and one day, worried about Yeon-seo's well-being, she visits her home when she can't even get in touch. Near the house. Se-jin is taken aback by the sight of Yeon-seo, who is so drunk she can hardly stand, and hurriedly takes her home. As they ride the elevator and open the front door, Yeon-seo utters a woman's name that Se-jin has never heard before, accompanied by a beautiful smile. Se-jin feels a strange sense of dissonance at Yeon-seo's soft voice calling her 'Kim Min-ha' and is confused when Yeon-seo suddenly kisses her. It has been nine years. The duration of the solid friendship tower built by Go Yeon-seo and Yeo Se-jin. And now, that long-standing friendship tower is shaking. It might be destroyed into pieces, leaving no trace behind, in a dangerous storm. Go Yeon-seo and Yeo Se-jin. Yeo Se-jin and Go Yeon-seo. Can they truly protect the tower of friendship? Or will they build a tower named love in the place where friendship has collapsed?