Paihame Kazoku OVA

Suika, a teenage girl who runs a “sugar dating” account under the alias “Melon” to make money off older men by showing her large breasts with strict no-touching rules, meets a client named Masuo — an overweight otaku who immediately violates her boundaries. He discovers her nipples are anatomically capable of being penetrated and proceeds to “nipplefuck” her against her will, leaving her breasts aching with lingering pleasure afterward. Masuo manipulates her into a second meeting by claiming only he can fix the sensation, then rapes her vaginally and reveals she is now addicted and effectively his property. The encounter turns sinister when Masuo casually calls her by her real name “Suika” as he leaves, revealing he somehow knows her true identity.