The explanation

'Hello students!' A man appears on the screen.

'You may not know me but I am a newly announced Minister of the Fertility. As you probably know there is a large scale problem with birth caused by an accident with the vaccines. To prevent the extinction of our nation we had to take drastic measures to increase the birth rate.' He continues.

'Starting today, everyday you will be having what we would like to call 'fertility seances'. This is a special room designed for this purpose. It features a one-way mirror in the middle of it. Some of you may have noticed that there are two of you inside.' He finishes this sentence with a uncomfortable smile.

Suddenly you realize that there is someone else on the other side of the mirror, probably a boy. You back away from the mirror and try to cover yourself with your hands. The announcer continues.

'Studies have shown that ejaculating once a day for a week increases a chance for impregnation three times. This effect doesn't last long though so the men have to keep doing this. Now I will tell you about the rules.' You listen carefully as he explains it.