Mona has been tasked with caring for her husband's father, Osamu. Until now, she had left it entirely to the housekeeper, Shiori, so Osamu was very happy about this. It seemed like they would live happily ever after, but one day, Mona finds out that her husband and Shiori are having an affair. Mona becomes emotionally unstable, and while caring for Osamu, she begins to have special feelings for him...