It all began with the delusion of his older brother, and his younger sister's rebellion began... Night after night, his younger sister "Ryoko" fell into a sex slave after being repeatedly trained. A sister who is like a sample of an honor student becomes an outlet for her brother's abnormal libido and pervertedness blooms. Panting with spanking, holding his own cock to the back of his throat, and happily accepting his brother's sperm in his vagina with an ecstatic expression while being tied up.