Two close sisters come from the countryside to visit their beloved uncle who lives in the city during summer vacation. The older sister, Ao, is a precocious brat with a brimming sexual curiosity, while the younger sister, Kina, is ignorant, quiet, and spoiled. The uncle is confused by her precocious questions and flustered by the glimpses of her panties. When the aunt is not careful, she teases and plays pranks on the uncle, who is at her mercy. He loses control over her sweaty, sun-tanned body and his reason begins to crumble...