She looks like a child! But her body is that of an adult! Her younger sister, Mao, has H-cup breasts but is still developing. She has zero knowledge about sex and even wears cotton underwear. But she can't stop being interested in the naughty things she's just started to learn about recently! With just a little knowledge, she seduces her sister's boyfriend with a panty shot! The impressive stain on her childish panties is adult juice! Filled with greenhorn pheromones, she instinctively lets her first experience be reverse cuckold sex! She gets turned on and has sex at night while wearing the first sexy lingerie she bought! Now she's part of the naughty adult world!