Japan is voting in an election for the upper house that is seen as a referendum for Japanese Prime Minister Shinzo Abe's policies.
Abe's ruling coalition looks to be headed for a comfortable victory despite doubts about his economic policies.
A strong showing may open the door for Abe and his party to reform the post-war, pacifist constitution, a long-standing goal of the prime minister and his Liberal Democratic Party.
Revising the charter needs the approval of two-thirds in both houses of parliament and a majority in a referendum.
"I think the main issue this election is the revision of the Constitution. But, during the election campaigns, (Abe) chose to divert his focus towards the economic issues, which makes me worry that if the Liberal Democratic Party stays in power, Japan may soon become a country which will be able to go to war," said voter Nagisa Kato.
Abe's goal of increased militarism is strongly opposed by many Japanese, especially in light of the U.S.-Japan security alliance. Thousands of people protested U.S. military presence on the island of Okinawa last month.
Media surveys have shown the ruling bloc is set to exceed Abe's target of 61 seats while his LDP could win a majority on its own for the first time since 1989.
A big win would allow Abe to assert he has a mandate for his economic and other policies, but any such claim would be undermined if turnout is low.
The 2014 election for the lower house saw a record low turnout of 52.66 percent.
Voters will elect half the seats in the 242-member chamber.