But although Japan's increasingly sexless society has led to the lowest birthrate in the developed world, sending the number of live births below 1 million last year, the lowest level in modern history, it's the rising number of deaths that are causing the rate at which Japan's population is shrinking to accelerate.

According to the FT, those born during a pre-WWII baby boom, which was fostered by the Imperial government during the run-up to the war, are rapidly reaching the end of their lives. And the death rate in the country, which last year outstripped the number of births by roughly 430,000, is expected to accelerate through 2030.

"The reason Japan's population is now falling so fast is not the low birth rate but rather an increase in the number of deaths," said Akihiko Matsutani, professor emeritus in applied economics at the National Graduate Institute for Policy Studies.

Japan had a baby boom before the second world war because of military pressure to increase the birth rate, he added. "Those people are now reaching the age of passing away," said Prof Matsutani.