Prime Minister Shinzo Abe, seeking to allay concerns he would divert energy from fixing a fragile economy to revising Japan's pacifist constitution after a big election win, says changing the charter won't be easy.
Mr Abe's coalition and allies won two-thirds of the seats in parliament's upper house in Sunday's election (local time).
That victory, with the ruling bloc's super majority in the lower house, opens the door to revising the constitution for the first time since its adoption after Japan's defeat in World War Two.
China's official agency quickly warned that the victory posed a danger to regional stability.
Commentaries by the Xinhua news agency are not formal government statements but often reflect official thinking in China, where memories of Japan's past militarism still spark outrage.
Mr Abe said revising the constitution was his Liberal Democratic Party's cherished goal, but forging agreement on changes in the diverse pro-revision camp would not be easy.
Revisions require a two-thirds majority in both houses of parliament and a majority of votes in a public referendum.
"To realise revision of the constitution is my duty as LDP president," Mr Abe told a news conference.
"But it is not that easy, so I hope debate will deepen steadily."
Experts agreed that building such agreement would be tough.
"It's the first time to have two-thirds in both houses of parliament, but you can't find any issue on which the two-thirds can agree," said Gerry Curtis, professor emeritus at New York's Columbia University.
Some in financial markets worry a focus on the constitution would drain attention from the economy, but Mr Abe promised on Monday (local time) to craft a large stimulus package.
Doubts about Mr Abe's policies persist even though his ruling bloc won big in terms of the number of seats.
Many voters felt they had no other option, given memories of the main opposition Democratic Party's rocky 2009-2012 rule. Others stayed home.
Surveys show many Japanese voters are wary of changing the constitution's war-renouncing Article 9, which advocates see as the source of Japan's post-war peace and democracy.
Conservatives see it as a symbol of humiliating defeat.
If taken literally, Article 9 bans the maintenance of armed forces.
Successive governments have interpreted it to allow a military for self-defence, a concept Mr Abe last year stretched to allow Japan's military to aid friendly nations under attack.
Formal revision of Article 9 would likely be largely symbolic - though nonetheless historic.