DRPT-098 Miu Arioka and Akana Ito: sister discovers sensitive nipples and teases in revenge

A younger sister who is always mocked for her small breasts sees her chance when she finds her older sister asleep by the front door late at night, and she quietly rubs the older woman's nipples, noticing how sensitive they are. The next day, she sneaks up behind her sister during a phone call and licks, sucks, and rubs her nipples until the older sister cums, humiliating her as a weak-nippled woman. The older sister, now aware of her sensitivity, ends up masturbating her nipples in the bathroom.