A new erogenous zone, the "pilum muscle," has been discovered in women's buttocks! [※What is the pilum muscle? ...It is a muscle located in the deepest part of the buttocks, closely connected to the nerves. With special stimulation, it becomes the most sensitive erogenous zone on a woman's body, surpassing even the nipples and clitoris.] Wakana Nao, who has an exquisite body, attempts to develop the pilum muscle for the first time in AV history. Although she is skeptical at first, as she receives a special massage from an expert, a stain gradually appears in her crotch! When the pleasure exceeds her limits, she convulses violently, wets herself in ecstasy, and climaxes over and over again with pilum sex! The mysteries of a woman's buttocks are revealed for the first time!