Horny, carefree Rino complains to a male friend that her boyfriend refuses sex. He suggests her huge breasts or poor technique may be the problem, somehow turning the conversation into a practical test. Her shy tongue work passes, but the issue remains, so a later experiment goes further. She protests that it is pointless and would count as cheating, yet frustration makes her happily surrender to being stripped, touched, licked, and sucked amid playful banter.