Kasumi's Sex Crisis.

After her mother left the family, Kasumi lived with her stepfather. One day, Kasumi’s stepfather can no longer control himself and starts having sex with Kasumi. Although this happens regularly from then on, Kasumi does very well at school. Kasumi’s teacher tells Kasumi’s stepfather that the university in Tokyo that she wants is now within reach. To prevent Kasumi from moving away to Tokyo, her stepfather offers to pay for Kasumi to study nearby, and he has another idea as well…