Aigan Chikubi Doubutsu

Ria appears to be a demure and popular girl in her class, but she hides a secret life as a masochistic toy trained by an older man. Her nipples have been conditioned to become exceptionally long and sensitive, a direct result of her intense training. She is subjected to a full course of torment designed to break her will and reinforce her place as a mere pet.

The older man crushes, twists, and pulls her sensitive nipples, pushing her to her limits. Through this relentless abuse, Ria is forced to confront her true nature and accept that she is nothing more than a nipple animal, a plaything for his pleasure.