The so-called outreach programme involves Chad, Indonesia, Sri Lanka, Bangladesh, Papua New Guinea, Vietnam and Laos.
G7 host Japan said ahead of the meeting that it would zero in on Asia's stability and prosperity including "open and stable seas" as well as United Nations sustainable development goals, with a focus on Africa.
The reference to maritime issues comes as tensions build over Beijing's claims to almost the entire South China Sea, a strategic body of water that encompasses key global shipping lanes.
At the close of their formal session in Ise-Shima, G7 leaders fired a broadside across China's bows over its behaviour in the region, without mentioning Beijing by name.
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"We are concerned about the situation in the East and South China Seas, and emphasise the fundamental importance of peaceful management and settlement of disputes," the summit-ending statement said.
Beijing is also locked in a dispute with G7 host Japan over rocky outcroppings in the East China Sea, stoking broader concerns about Beijing's growing regional might and threats to back up its claims with force, if necessary.
The roster of countries Beijing claims back its position on the South China Sea includes Mauritania, Togo and land-locked Niger.
Also participating in today's sessions were UN Secretary General Ban Ki-moon, International Monetary Fund chief Christine Lagarde and World Bank head Jim Yong Kim.
The heads of the Organisation for Economic Co-operation and Development and the Asian Development Bank also attended.