Her sister is always teased by her sister because of her small breasts, and she always wants to find a chance to get back at her sister! Late one night, she found her sister sleeping in the foyer! She secretly stroked her sister's nipples and found that they were unusually sensitive! The next day, her sister was on the phone with her boyfriend, when suddenly someone approached her from behind ...... caressing, licking and sucking her nipples, and the skillful tongue technique soon brought her to orgasm, turning her into a sister with sensitive nipples! After realizing that her nipples are very sensitive, her sister masturbates in the bathroom...