A month earlier he had separated from his wife, but she was the one who checked up on him after employees of his financial services and immigration consultancy noted their chief executive had been absent without notice for three days.
In May the coroner, electing not to open a formal inquiry into the death, ruled the businessman had died of "complications of chronic alcoholism".
There were double-takes to ensure the chief suspect hadn't staged an elaborate ruse.
"We met with a number of Japanese investors, where it was raised whether he was actually dead or not," said Grant Thornton partner Tim Downes, who is managing the liquidation.
"One of them said he definitely was, because he had attended the funeral."
Downes said he was poised to ask whether the service on February 26 at the North Shore Memorial Park Chapel was open casket, before the investor pre-empted him by saying he'd conducted inquiries of his own.
"[The investor] said, 'I lifted up the casket and took a photo of him. He was looking less healthy than usual, but it was him'."
Downes described "the labyrinth" of seven companies comprising the East Winds group since being appointed in April. He said in reports that only $1m had been recovered to date and a "significant amount of funds had been paid to related entities".
In an interview with the Herald Downes was even more direct and said the end of the charade came soon after the end of its founder.
"It's a Ponzi scheme you know — money coming in was used to pay interest and payouts for existing investors — but suddenly he died and the whole thing collapsed."
Downes said the dual immigration and financial services businesses offered a synergistic modus operandi, where Tanaka claimed funds placed with his East Winds could help qualify applicants for investor visas.
"The Japanese investors are obviously alarmed and very distressed. We're looking to give them comfort, but it's going to be quite a drawn-out process and I can understand how they feel,"
Information given to the Herald by investors show Tanaka was last year claiming business investments internationally, using Cayman Islands special purpose vehicles managed by Hong Kong fund managers.
Downes said his investigation was now also looking overseas and following leads suggesting investor money may have ended up in offshore accounts or properties.
Downes' first report on the group said record-keeping was haphazard at best.
"There is no orderly manner to the records, the records are set out in a mixture of Japanese and English and we have identified a number of inconsistencies."
Translations of marketing pamphlets showed East Winds touted a kiwi dollar-yen foreign-exchange trading scheme called the Waterloo Fund which claimed to deliver returns, of 1 or 2 per cent a month, by buying low and selling high.
Unusually, as the performance of such funds are by nature volatile, Waterloo offered investors fixed-term returns ranging from 8 per cent over one year, or 12 per cent for those who locked their funds in for three.
Downes said the case was unusual in that it appears investors had no clue anything was wrong until February: "This has gone on for so long, but it was only after he passed away that alarm bells ring."
East Winds operated almost exclusively in the Japanese community, with no website or marketing material in English, perhaps explaining how the metastasising scheme operated unchecked for potentially decade.
The Serious Fraud Office confirmed receipt of complaints from investors, but said it had "nothing further to add at this stage".
The Financial Markets Authority said "we are not currently investigating these companies".
Downs said NZ police had also been in touch, acting on complaints from investors. But the case of the dead man and the missing millions was unusual in that typically unravelling big fraud cases involved building a criminal case against a fugitive.
"In a normal situation you've got the guy off the coast of Capri, on his yacht, and its all closing in on him, and it's about bringing them to account."
New Zealand's largest ever Ponzi scheme was orchestrated by Wellington financier David Ross. The former head of the Ross Asset Management was jailed for 10 years and 10 months in November 2013, having defrauded more than 700 clients of $115.5m.