Kibaru became pregnant at a young age and gave birth to Tatsuaki. Because they were close in age, the two were unusually close. On days off, they would go shopping or traveling together, feeling more like friends than parent and child. One day, Tatsuaki invited Kibaru on a hot spring trip using his university summer break. As usual, Kibaru looked forward to enjoying the trip with him. However, Tatsuaki had invited her on the trip to convey something important.
