Big Sister Little Brother Fucking Seminar Creampie Special.
The low birth ratio in Japan continues to be a problem, and even more, males are remaining virgins to much older ages.
To curve these problems, SOD organizes this seminar and invites both the guy and her sister. Because these guys are so bad at interacting with women that a girl they can be comfortable with is required.
Then, they perform a series of creampie experiments and exercises.