Last Friday the Abe Government shifted publicly towards a more favourable position on foundation membership of China-backed Asian Infrastructure Investment Bank.

This follows dramatic developments during the week as Germany, France and Italy followed the UK's sudden lead in committing to the AIIB, with more favourable reassessments under way in Australia and South Korea too. Cascading interest in joining is in response to Beijing's insistence that founding membership of the AIIB be finalised this month. The UK's decision came in for criticism from the US.

Japan has shared American concerns that the AIIB plan is aimed at enhancing Chinese influence in the region, and that it will be at cross-purposes with the IMF, World Bank, and most notably, the Asian Development Bank. The latter has long been significantly influenced and supported financially by Tokyo and by custom has been headed by a Japanese. Current Bank of Japan governor Haruhiko Kuroda, principal architect of the massive quantitative-easing component of 'Abenomics', served as ADB president for eight years prior to heading up the BoJ. Kuroda has spoken publicly of the ADB's long-established know how and that it should continue to be used.

In a sitting of the Diet's budget committee, an opposition lawmaker quizzed Prime Minister Abe on whether Japan was in danger of being left out as other nations lined up to join the AIIB. Abe said his Government would consider membership if it could be assured of transparency in the AIIB's governance. Abe, perhaps a little disingenuously in light of concerns about China's motivations in proposing the AIIB, stated that it might present an opportunity to integrate China, now the second largest economy in the world, into a cooperative rules-based international order.

Finance Minister Taro Aso also left the door open to membership, saying that Japan wanted assurances on standards of governance and financial sustainability. In particular, he said the board of directors should have direct oversight of loan decisions. He said Japan had not yet received replies to the questions it has posed. Chief Cabinet Secretary Yoshihide Suga struck a more cautious note, reflecting divisions of opinion and general wariness within the Government and bureaucracy on whether Japan would have influence within the AIIB while lending legitimacy to it through membership.

Japanese policymakers remain sensitive to arguments about the primacy of existing international institutions after Japan's proposal for a new regional fund in the wake of the 1997-8 Asian financial crisis was stymied by Washington as needlessly impinging on the IMF's brief.

Some Japanese media commentary suggested rising private sector concern that business opportunities in regional infrastructure provision, long a national competitive strength, might be lost if Japan stayed out of the AIIB. Australian Treasurer Joe Hockey is speaking openly of how the Abbott Government wants Australian businesses to get work from the AIIB. The race for such opportunity puts both Washington and Tokyo in an an awkward position in relation to the AIIB.

The AIIB issue has arisen at a time of quiet in China-Japan relations following the meeting between Shinzo Abe and Xi Jinping on the sidelines of the APEC summit in Beijing in November 2014. But the approaching 70th anniversary of the end of the World War II, and Abe's ongoing deliberations about developing an official statement, means this quiet period comes with  a clear end-date. There is considerable foreboding in Tokyo about Beijing's expected demeanour come August and beyond.

In other news from last Friday, the ruling Liberal Democratic Party reached formal agreement with its small coalition partner Komeito on the terms and timetable for introducing legislation to permit greater involvement by the Self Defence Forces (SDF) in collective security arrangements. As anticipated, the pacifistic Buddhist Sokka Gakkai-affiliated Komeito received undertakings on the limited conditions under which the SDF might deploy force.

Friday also marked the twentieth anniversary of the Tokyo subway sarin gas attacks, carried out by the religious cult Aum Shinrikyo. A memorial service was held at the Kasumigaseki subway station at the heart of the national bureaucratic district, which had been targeted by Aum in what is now depicted in Japan as the world's first chemical weapon terrorist attack. The Aum sarin attacks highlighted how Japan's post-war decentralised policing structure hampered investigation. Subsequent reforms were tentative.

In sum, Friday brought multiple reminders that post-war Japan has not been a 'normal' country in terms of its state capacities to police, defend, or even gather intelligence at home and abroad, as well as to involve itself in international aid and development. The Japanese take institution-building seriously, as they feel so heavily the constraints of them at home.

Also on Friday, school holidays started for many; the academic calendar is calibrated to start and finish with the brief fragile beauty of the cherry blossoms. Springtime in Japan is deeply culturally associated with the permanence of impermanence. Thoughts turn to what is constant, and what is to be memorialised. It is a time of anticipation, of new starts in school and work. Yet the weather is typically unsettled and spring defies use as a metaphor for unambiguously positive change.