Yuu is staying at his relatives' house for a week during summer school. However, he can't concentrate on his studies because of his aunt Maki's defenseless appearance, and he masturbates in frustration... Maki is captivated by his aunt's young and strong cock, and uses him to release her daily sexual desires that cannot be satisfied by her husband alone. Then, Yuu is attacked by her and feels sexual awakening. He loses himself in the pleasure and starts violating Maki like a monkey. She becomes more and more absorbed in her nephew's endless and reckless sexual intercourse...