Mama Katsu: Midareru Mama-tachi no Himitsu. Yoshiya is a charismatic and good-looking man, who works as a teacher and satisfies the needs of aunties. He likes his own sister and he had parted ways with his sister due to his disappointment at seeing her marry another man. Since her sister's husband was traveling for work, she went back to live with her sister while planning to have sex with her sister with the help of one of the aunties named Touka with whom she had frequent contact.