Thousands of demonstrators assembled outside Japan's National Diet Building in Tokyo on 20 May to protest the government's drive to revise the country's pacifist constitution and expand its military capabilities. Organisers estimated the crowd at roughly 10,000 people, making it one of the most visible shows of public opposition to Prime Minister Sanae Takaichi's security agenda this year.

What Protesters Demanded

Demonstrators carried placards bearing messages such as 'Stop constitutional revision and military expansion' and 'Do not destroy Article 9,' while chanting 'Stop missile deployment' and 'Takaichi must resign.' The breadth of the slogans reflected opposition spanning both constitutional and operational defence concerns.

Yuki Hoshino, one of the participants, said the public does not want constitutional amendments and that the Takaichi administration is advancing the agenda without adequate public consent. 'So many people have gathered here (to protest), hoping that (the government) will change its mind,' Hoshino said.

Another protester, Ryosuke Tanji, invoked Japan's wartime history. 'Absolutely no war should be allowed to happen,' he said. 'Japan committed terrible acts in the past, and perhaps many Japanese are gradually forgetting that history. But the more I learn about it, the more strongly I feel that such things must never happen again.'

Academic Voices at the Rally

Hiroshi Onishi, professor emeritus at Keio University, argued at the rally that the government's military buildup directly contradicts the pacifist principles enshrined in Japan's constitution. His presence alongside ordinary citizens underscored the cross-sectoral nature of the opposition.

The LDP's Proposed Security Revisions

Japanese media reported on Monday that the ruling Liberal Democratic Party (LDP) had drafted proposals to revise Japan's three key national security documents. The proposals reportedly call for strengthening Japan's air defence systems and sustained combat capabilities, as well as the early deployment of submarines equipped with advanced propulsion systems and designed to carry long-range missiles — measures framed by the government as bolstering Japan's so-called 'counterstrike capabilities.'

What Article 9 Says and Why It Matters

Japan's current constitution, which took effect in 1947, contains Article 9 — under which the country renounces war as a sovereign right and the threat or use of force as a means of settling international disputes. The article also stipulates that Japan shall not maintain war potential, earning the document its global reputation as the 'pacifist constitution.'

Takaichi and other right-wing factions within the LDP have long advocated revising Article 9. The prime minister has repeatedly expressed her support for constitutional revision this year, reportedly drawing growing concern across Japanese civil society, academia, and opposition parties. This comes amid a broader regional security debate, with Japan having already approved a record defence budget increase in recent years. Whether the LDP can muster the parliamentary supermajority required for a constitutional referendum remains an open question.