The head of the Narumiya family, 'Tetsuo,' is a strict father. Naturally, his eldest daughter, 'Urumi,' and younger brother, 'Ma-kun,' were raised strictly as well. One day, Ma-kun, who had started to become interested in sex, was caught by his parents with an erotic book he had borrowed from a friend and got severely scolded. Urumi, feeling sorry for her brother, decided to educate him about sex using her own body…
