Due to work, Mitsuru has been living alone in Tokyo for three years. On một visit to the doctor, he discovered that he had a tumor in his body. Thinking he didn't have long to live, he took his beloved mother on a trip to enjoy some joyful days before his death. They both went to a hot spring hotel. Mitsuru had secretly loved his mother for a long time. So when his mother got drunk and revealed her beautiful underwear in front of him, he couldn't help but touch and explore her body. His mother woke up and stopped him, and Mitsuru told her that he didn't have long to live. Out of compassion for her son and wanting him to fight his illness, Aoi agreed. When they returned, Mitsuru went for a check-up again. It turned out that it was just a benign tumor, and due to the doctor's serious expression, he had misunderstood. After this, the relationship between mother and daughter got better and better, even though it was no longer life-threatening, Aoi still agreed to let Mitsuru have sex with her, even though she knew that this was wrong...