The little sister who is always made fun of for her boobs was looking for an opportunity to retaliate against her older sister! One day, she discovered her older sister sleeping at the entrance late at night! When she secretly poked her nipples, she had a sensitive reaction! The next day, while her older sister was on the phone with her boyfriend, she was creampied from behind… with the little sister's tongue technique, she was quickly cumming and turned into a weak nipple big sister! The older sister, who had been made aware of her sensitivity, was masturbating her nipples in the bathroom when her little sister suddenly burst in! While laughing, she teases her older sister's nipples and develops them day after day! The little sister, who tortures her older sister, who has become too sensitive with various plays such as pushing her back against the backrest and ice torture, but in the end, the older sister tortures her little sister's nipples…