After separating from her husband, Miina has been raising her son Kota on her own. Although she is a good mother who is dedicated to education, she does not notice her son's growth as a man. Kota begins to take an interest in the female body rather than in his studies, and becomes aroused by Miina's body while she sleeps, and plays with it. When Miina realizes the need for sex education, she uses her own body to teach him the Iroha of sex, step by step. How to touch breasts, how to handle the female genitals, and even penetration... A gentle and careful sex lesson that only a mother can give.