Japanese voters are casting ballots in national elections Sunday, a first big test for Prime Minister Fumio Kishida to determine if he has a large enough mandate to tackle a coronavirus-battered economy, a fast-aging and dwindling population and security challenges from China and North Korea.Japanese voters are casting ballots in national elections Sunday, a first big test for Prime Minister Fumio Kishida to determine if he has a large enough mandate to tackle a coronavirus-battered economy, a fast-aging and dwindling population and security challenges from China and North Korea.