Morio Kiyomi was the subject of envy, when she married Dr. Yanagisawa Shigero, the owner of Yanagisawa Clinic. Although the marriage brought her status and wealth, Kiyomi was not blessed with children. The couple then decided to go through the In Vitro Fertilisation program, and soon Kiyomi successfully gave birth to a little baby. Unfortunately, the baby was born with an illness that can only be cured through stem cell transfer, and so the Yanagisawas decided to have another baby in order to save their existing child. However, Kiyomi's body is too weak to have another child, and so she approaches her estranged younger sister, Manami, to be the surrogate mother. Unbeknownst to Kiyomi, Manami is actually very bitter about her good fortune in landing a rich man, and is plotting vengeance on her.