"Huh? Is this girl... slow? She doesn't resist when I touch her... This means I can do whatever lewd things I want!" On a humid summer day, my niece Rina-chan came to stay over. In a few years, she had grown unexpectedly cute and busty, but her personality was still the same as before! From playing erotic pranks during her naps to taking baths together, and spending days filled with breast-rubbing creampie sex, Rina-chan, who was initially unresponsive, gradually begins to feel pleasure! I'll savor every inch of my defenseless and resistant niece's busty body!