The G7 is a group of countries that share the same values of valuing freedom and democracy and have great influence in the world in terms of politics, economics, and military affairs.
At the G7 Summit, heads of state and government exchange views on various global issues. The G7 Summit aims to take a leadership role in the world and to work together to effectively resolve issues.
In addition to the seven countries and the EU, invited countries and international organizations may also participate. However, even if a policy is decided, there is no compulsion for countries around the world to follow it.
The Summit was started in 1973 in the wake of the oil crisis, which led to a global economic recession due to rising oil prices and other factors. The first summit was held in 1975 with the United States, the United Kingdom, Italy, Germany, Japan, and France, followed by Canada in 1976 and the European Community (EC, now the EU) in 1977. In 2014, following Russia's annexation of the Crimean Peninsula in Ukraine, participation was suspended, and the group reverted to the G7.
The topics of discussion, initially economic and energy issues, have gradually broadened to include climate change and counterterrorism.

Of the countries participating in the G7, the U.S. had the highest total value of Japanese exports and imports. Compared to the other five countries, this is by far the largest amount, indicating that the U.S. and Japan have strong economic ties. Japan exports automobiles, automobile parts, aircraft engine parts, and construction and mining equipment to the United States. On the other hand, Japan imports pharmaceuticals, oil and natural gas, and aircraft engines from the United States.
The second largest exporters are Germany, Canada, the United Kingdom, Italy, and France, in that order. Each country has its own characteristics in terms of what it trades and the balance between exports and imports. Please take a look at the ties between Japan and the G7 countries in this article, which summarizes the economic, cultural, and political aspects of the ties.

The top 10 countries and regions with which Japan traded in 2022, not just G7 countries, are listed below in terms of the total value of exports and imports. The ranking of unranked G7 countries is also given.
(Source: Trade Statistics, Ministry of Finance; amounts are rounded down to the nearest 100 million yen; boldface figures indicate G7 countries)

No. 1 China = 43.847 trillion yen
No. 2 U.S.A. = 29.9881 trillion yen
No. 3 Australia = 13,784.4 trillion yen
No. 4 Taiwan = 11.9545 trillion yen
No. 5 South Korea = 11,522.4 billion yen
6th Thailand = 7,771.6 billion yen
No. 7 United Arab Emirates = 7,134.3 billion yen
No. 8 Saudi Arabia = 6,236.7 billion yen
No. 9 Vietnam = 5,929.3 billion yen
No. 10 Indonesia = 5,739.7 billion yen
14th Germany = 5,556.5 billion yen
No. 17 Canada = 3,301.1 trillion yen
No. 21 United Kingdom = 2,352.4 trillion yen
23rd Italy = 2,238.6 billion yen
24th France = 2,168.7 billion yen

Ministry of Finance Trade Statistics: https://www.customs.go.jp/toukei/info/

G7 Hiroshima Summit 2023: https://www.g7hiroshima.go.jp/
Basic Q&A on the G7, Ministry of Foreign Affairs of Japan:
https://www.mofa.go.jp/mofaj/gaiko/summit/ko_2000/faq/index.html
Tadokoro, Masayuki, "G7 and G20 in Global Governance: Retrospect and Prospects:
https://www2.jiia.or.jp/kokusaimondai_archive/2010/2019-01_002.pdf?noprint