Adachi City Council chairman Go Senuma said the group arrived on August 1 and instantly received a warm welcome.
It was his first visit to Belmont and he said he intended to promote Australia as a safe, friendly and warm country that everyone should visit.
The group also toured the South West, visiting Surfer’s Point in Margaret River which Mr Senuma said he would recommend to surfers in Japan.
He hoped to use the tour to further build a strong relationship between the countries.
Mr Senuma said Adachi and Belmont were of similar size but Adachi housed up to 700,000 residents.
The city’s function room was filled with Japanese and local community leaders including Belmont MLA Glenys Godfrey, some city councillors and students who will visit Japan in January.
The luncheon guests were treated to a song by Mr Senuma accompanied by a dance performed by the Japanese visitors, ahead of a final address by Belmont Sister City Association chairwoman Madeleine Rennie.
Ms Rennie had received a Certificate of Commendation from Japan’s Foreign Affairs Minister Fumio Kishida for her work to strengthen ties between Australia and Japan.
St Norbert College student Bryce Hellmrich acted as interpreter for the event which finished with a traditional hand-clapping ceremony before Mr Senuma embraced chief executive Stuart Cole on stage.