The J-style younger sister who can't quit sucking fingers. Her innocent gestures from childhood, which once seemed cute, now make her older brother feel strangely aroused as she grows up. One day, after seeing her older brother's erect cock, the younger sister jumps at him, wanting to suck it. Her older brother discovers that she has a special constitution where her pussy gets wet just from sucking, and he can't control his excitement, plunging into sex. Soon, the younger sister becomes addicted to sucking, to the point where her pussy gets wet even after brushing her teeth...