Since separating from her husband, Ryo has been single-handedly raising her only son, Makoto. Using her ex-husband, who struggled financially, as a negative example, Ryo gives Makoto an education that could be described as excessive, with an eye to his future. However, as Makoto reaches an age of marriageability, he gradually becomes consumed by sexual desires and loses focus on his studies. Thinking of his son's future, Ryo relieves his desires through oral sex, even though he knows it is taboo. However, this act also ignites Ryo's own hidden desire. The sex education escalates, and he goes beyond teaching Makoto about the structure of the female body, teaching him the sensations of the female genitals, and even engaging in intense, real sex...