A woman named Aika lives with her husband and son, Junya, who is around the same age. One day, Junya breaks his arm in a fight with a friend, and Aika starts taking care of her son who needs assistance. However, Aika finds herself becoming aware of her son's body as he grows into an adult, and she inadvertently gives him a lesson on his innocent penis. As a result, Junya can no longer suppress his interest in sex... Feeling responsible, Aika then teaches him the basics of sex thoroughly with her own body as a mother.
