A shy son brings a friend home for the first time. It turns out that his friend, Shunya, is an honor student, well-trusted by his teachers, and a central figure in the class. His mother, Serino, is delighted that he has made a good friend and warmly welcomes him, but Shunya's real goal is Serino's body. Shunya has long been attracted to Serino's beauty, so he first wins over his son, and then finally makes his way to the main castle. Serino, unaware of this, is completely fooled by his personality and is overcome by her depraved desire...