During summer vacation, my nephew Satoshi came to visit my aunt's house, which I had admired since I was little. I was secretly pleased to be alone with my aunt while my uncle went on a long business trip. However, her aunt finds out that she is a virgin and is teased, "I'll let her lose her virginity." With half a prank on her big breasts, Satoshi's rationality is cornered to the point of collapse...