Japanese Prime Minister Shinzo Abe received Hasina on her arrival at the Shima Kanko Hotel in Ise-Shima city on Kashiko Island on Friday morning.
Later, the Bangladesh prime minister, along with leaders of G7 nations – the United States, United Kingdom, Canada, France, Germany, Italy and Japan – and other countries joined the inaugural session.
Sheikh Hasina will convey South Asia's message to the seven industrialised nations.
G-7 invites countries outside the grouping to the outreach meetings to discuss regional development.
The Bangladesh prime minister will attend two sessions and join luncheon on Friday. Later, she will hold a meeting with Cameron at noon.
Sheikh Hasina's sister, Sheikh Rehana, Foreign Minister AH Mahmood Ali, senior Awami League leader Akhtaruzzaman and a delegation of 30 businessmen led by the FBCCI President Abdul Matlub Ahmad are accompanying the prime minister.
During her four-day official visit to Japan, the prime minister will hold meetings with Abe and Sri Lankan President Maithripala Sirisena.
Hasina will fly to Tokyo from Nagoya at noon after attending the Outreach Meeting. She will inaugurate a new chancery building of the Bangladesh Embassy in the Japanese capital.
The FBCCI and Japan External Trade Organization (JETRO) are supposed to sign a memorandum of understanding on Sunday.
The prime minister is scheduled to leave Tokyo for Dhaka on Sunday evening after joining a reception given by expatriate Bangladeshis.