The younger brother, who has come to live with his older brother and his wife, is aroused by his older sister's sex appeal and looks at her every day. One day, he witnesses his older sister sucking the dick of one of his brother's students, who is a teacher. Unable to resist, the younger brother approaches his sister, and she responds like an adult, gently taking his brother's hard cock into her mouth. The older sister and brother awaken to a forbidden relationship and become immersed in pleasure.