Shiho feels discomfort in her anus and, swallowing her pride, visits the clinic for an examination. However, the doctor in charge is a perverted physician with a huge cock who became an anorectal specialist solely to satisfy his own sexual desires. Shiho is subjected to humiliating anal-focused acts by the doctor and female nurses, forced to live as a mere sex toy for their gratification. Over time, she gradually transforms into an anal-addicted woman. This change etches itself not only onto her body but deep into her mind as well.