Japanese ambassador Shingo Yamagami returns to Tokyo on April 29 after 'putting in 120%'

The high-profile diplomat said he's proud of his work improving the Canberra embassy's work ethic, adding he was told his predecessors played video games and golf most of the week.

Mr Yamagami confirmed with The Canberra Times he will leave Australia on April 29, saying lightheartedly he will recuperate with a hot spring vacation and plans to write "a few" books.

The imminent departure means Australia will potentially be without a Japanese ambassador during the anticipated Quad summit held in Sydney next month.

Mr Yamagami, who arrived in late 2020 during the COVID-19 pandemic, said he had put in "120 per cent" since his first day, expecting his posting to be relatively short.

''[I thought] my time is going to be limited. I had to make that difference during that short time," he told The Canberra Times at the Sydney Dialogue forum on Wednesday.

"The turnover rate [for Japanese ambassadors] is very, very high. Especially to a country like Australia - there's a long queue of people who'd like to come here."

The first-time ambassador, and once Tokyo "spymaster", is a well-known figure in Canberra's diplomatic corps and is regularly seen mingling with politicians on both sides of the chamber.

But Mr Yamagami's diplomatic style has also been criticised by some former diplomats for being a "maverick" and unfairly critical of China.

Japan's Ministry of Foreign Affairs reportedly launched two inspections last year into Mr Yamagami's handling of the Empire Circuit embassy, according to the Australian Financial Review.

There has been speculation these inspections are partly behind his recall to Japan after two-and-a-half years at the posting.

The Japanese ambassador dismissed the claims, saying he was disappointed to see a number of media reports suggest he was being returned early.

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Mr Yamagami said the inspections were routine but hinted it was related to his push to make the embassy more efficient than his predecessors.

"Because of the fact that this embassy has been enjoying a relatively, sort of, free period, not stressful period, there was some room for improvement in terms of work morale and ethics," he said.

"I was told by Japanese residents in Australia and also Australian staff at the embassy, there were ambassadors who were playing golf four days per week.

"There were ambassadors toying with even PlayStation in their offices.

"I wanted to change the mindset of those diplomats."

Tokyo is likely months off announcing its next pick for the top envoy to Australia.

Mr Yamagami said he's ready to come back to the "front line" after his time off.

"I think I'm the youngest to become ambassador in Australia in the past 20 years," he said.

"I have a few more years to go in the public service."