Shuu's mother Kaede receives a letter from the Japanese government. In order to counter the declining birthrate the government has ordered her to become pregnant in one month. With her husband gone she's scared of having sex with a random stranger so she asks her son Shuu to be the father!

His sister then insists that if he's going to get their mother pregnant he needs to make a baby with her too. His childhood friend Kao-nee and her younger sister Renge refuse to be left out and insist on making babies with Shuu too!

But what about dating, romance, and marriage! Shuu refuses to make babies with any of the girls without love first so a race to capture his heart begins.