Rina tries her older step-sister's new swimsuit on without permission. She is caught and given a stern spanking on her bottom by the step-sister. However, she gets a chance for revenge with the step-sister's slip of the tongue. Then their step-mother returns home and finds her daughters' silly spanking session. The step-mom is furious and gives them both a harsh lesson they won't ever forget. Part three of Brand New Swimsuit.