Young-Woong is a psychiatrist (Kim Kyeong-Ik). He has been married to Soo-Hyun (Jin Hye-Kyung) for 10 years, but their love has waned and they now feel indifferent towards each other. One day, Soo-Hyun's daughter Haru (Ayaka Tomoda) appears before them. Soo-Hyun gave birth to Haru while she was studying in Japan. Haru carries a wounded heart from her boyfriend's betrayal. Soo-Hyun asks Yoong-Woong to treat her daughter. Through their consultations, Young-Woong begins to dream of more than just a doctor and patient relationship.

"There's a relationship no one should know about."