If ever there were a wake-up call for Japan, the second-most indebted nation, the death of Jiroemon Kimura is it.

On one level, Kimura is a good-news story. He was the last man born in the 1800s when he died on June 12 at the ripe, and some might say enviable, age of 116. When he was born on April 19, 1897, Queen Victoria still reigned over the British Empire and childhood killers such as tuberculosis and pneumonia limited life expectancy in Japan to 44 years. Kimura is one of several Japanese who won the genetic version of the lottery.

That gets us to the bad-news part of this tale, one that heightens Prime Minister Shinzo Abe's challenge. As Japanese live longer and longer, they are altering a worrisome calculus. The combination of the world's highest life expectancy, a public debt more than double the size of its $5.9 trillion economy and a below-replacement birthrate is the stuff credit-rating downgrades are made of. Japan's unbalanced demographics are straining its pension liabilities by the day.

Japan has about 40 centenarians per 100,000 people and has the world's highest proportion of elderly. Life expectancy is roughly 83, a figure that is expected to exceed 90 for women by 2050. The birth rate, meanwhile, is waning. That raises an indelicate question: who will pay a huge, and growing, national debt when there are fewer and fewer Japanese?

On any list of the challenges to Abe's revival plans, dubbed "Abenomics," Japan's demographic time bomb deserves a place near the top. Abe, as have his many predecessors since the early 1990s, wants Japan to grow its way back to fiscal health. His birthrate policy amounts to wishful thinking: if we build a more vibrant economy, babies will come.

When he strong-armed the Bank of Japan to agree to double the monetary base, Abe's plan was for investors to buy domestic stocks as a means of boosting national confidence. The latest lesson from the market (the Nikkei 225 Stock Average plunged another 6.4 percent today) suggests that Japan's debt load matters more than the architects of Abenomics realize. Markets want reassurances that Abe is at least considering ways to restore some balance between government liabilities and population trends.

Abe has an opportunity to do that tomorrow when he pledges to flesh out the third-element of Abenomics, the so-called third arrow. The first two -- massive central bank liquidity and fiscal pump priming -- cheered investors. But to make this grand scheme work, Abe must articulate how Japan will pay off more and more debt with fewer and fewer people.

Otherwise, the underlying tenets of Abenomics look more like a magic trick than a plausible growth strategy. It isn't clear Japan's government will have the same luck as centenarians such as Kimura.

(William Pesek is a Bloomberg View columnist. Follow him on Twitter.)