The demure-looking Ria, popular in class, is actually a masochistic female masturbation toy trained by an older man! Her exceptionally long, erect nipples are the result of her training, making them incredibly sensitive! Crush those sensitive, vulgar long nipples! Twist them!! Pull them!!! A full course of training to make her understand she's nothing but a pet nipple animal!!

(Source: Fanza, translated)

Note: Published in Comic Megastore Vol.2