Due to her unfortunate life, the once pure and kind-hearted Shin Joo-yeon (Kim So-yeon) has now become selfish and indifferent. So when her childhood sweetheart Joo-wan (Sung Jun) saw Shin Joo-yeon again after 17 years, he could hardly believe that this arrogant and shrewd woman was the woman he had always missed in his memory. One day, Shin Joo-yeon suddenly learned that Joo-wan, who had returned from abroad, would live in her home. Despite her strong protests, the reality could not be changed. At the same time, Shin Joo-yeon had just broken up with her boyfriend Lee Jung-ho not long ago. She mistakenly thought that Lee Jung-ho had fallen in love with someone else, so a conflict broke out with her former friend Oh Se-ryung (Wang Ji-won). As she got to know him better, Joo-wan saw the fragile heart under Shin Joo-yeon's strong shell and was determined to protect her well. But at this moment, Joo-wan discovered that Shin Joo-yeon actually liked Kang Tae-yoon (Namgoong Min). The kind Joo-wan decided to hide her feelings and help the two of them get together.