Two years ago, Kouta's mother died from an illness. Since then, his grandmother Shouko has been handling the household chores, and the three of them have been living together. Not wanting to make him feel pitiful even without his mother, Shouko has been diligently taking care of the housework. To comfort such a Shouko, Kouta, who was very close to his grandmother as a child, invited her on a hot spring trip. During the trip, Shouko saw her grandson's huge penis and felt an itch in her crotch for the first time in a long while...
