A joint statement issued after the summit meeting refrained from an explicit mention of China's recent declaration of a maritime air defense zone over the East China Sea.
But it was the backdrop behind the promise to cooperate to ensure "freedom of overflight and aviation safety in accordance with universally recognised principles of international law."
The summit marks 40 years of ties between Japan and the 10-member Association of Southeast Asian Nations, a resource-rich region of more than 600 million people.
Earlier today, Tokyo pledged 20 trillion yen (USD 19.2 billion) in aid to Southeast Asian nations over the next five years to help close the region's development gap and improve its disaster preparedness.
It also promised another USD 100 billion to support the Japan-ASEAN Integration Fund.
The Japanese side listed on its "urgent agenda" assistance for improved maritime security and more effective coast guards, help with cybersecurity and counterterrorism, closer communications connections and improved disaster preparedness and management.
But like Japan, several ASEAN countries have territorial disputes with China that remain potential flashpoints.
China's unilateral declaration last month of an air defense zone over islands in the East China Sea that are claimed by both Japan and China raised hackles across the region and concern that China might follow up with a similar zone in contested areas of the South China Sea.
Japan has been expanding investments across Southeast Asia, especially since 2012, when anti-Japanese riots flared in China after Tokyo nationalized a group of uninhabited islands claimed by both countries.
