For several years, Masato Kanda barely slept.
“Three hours a night is overkill,” he laughs, speaking to the BBC from Tokyo.
“I slept for three hours straight before I woke up but then went back to bed, so if you add them up I had a bit more.”
So why was this 59-year-old bureaucrat's schedule so arduous?
Until the end of July, he was Japan's deputy finance minister for international affairs, the country's top currency diplomat or yen tsar.
Key to that role was fending off foreign exchange market speculators who could spark unrest in one of the world's largest economies.
Historically, authorities have intervened to weaken the value of the Japanese currency. A weak yen is beneficial for exporters like Toyota and Sony because it makes products cheaper for foreign buyers.
But when the yen fell during Mr. Kanda's term, it raised the cost of imports of essential goods like food and fuel, sparking a cost-of-living crisis in a country more accustomed to seeing prices fall instead. than increase.
During his three years in this position, the value of the yen against the US dollar weakened by more than 45%.
To control the yen's fall, Mr. Kanda released about 25 trillion yen ($173 billion) to support the currency, marking Japan's first such intervention in nearly a quarter century.
“The Bank of Japan and the Ministry of Finance are very clear. They do not intervene at a particular level of the currency, but they intervene when market volatility is too high,” explains economist Jesper Koll.
Japan now finds itself on the US Treasury's watch list of potential currency manipulators.
But Mr. Kanda says what he did did not constitute market manipulation.
“Markets should move based on fundamentals, but they sometimes fluctuate excessively due to speculation, and they don't reflect fundamentals which don't change overnight,” he says.
“When it hits everyday consumers who need to buy food or fuel, that’s where we came in.”
While countries like the United States and the United Kingdom can raise interest rates to increase the value of their currencies, Japan has for years been unable to increase the cost of its borrowing due to weak of its economy.
Professor Seijiro Takeshita of Shizuoka University says Japan had no choice but to intervene in foreign exchange markets.
“It’s not the right thing to do, but in my opinion it’s the only thing they can do.”
The irony is that the value of the yen has surged in recent months without Mr. Kanda or his successor lifting a finger after the Bank of Japan surprised markets with a rate hike and the country had a new Prime Minister.
So was the $170 billion offer to prop up the yen a waste of money?
No, replies Mr. Kanda and emphasizes that his interventions have indeed generated a profit, although he emphasizes that this was never an objective.
As for whether his actions were ultimately successful, he says: “It's not for me to assess, but many say our foreign exchange management stopped the excessive level of speculation.”
Markets or historians should be the final judges, he adds.
After decades of economic stagnation, Mr. Kanda is also optimistic about Japan's prospects.
“We are finally seeing an increase in investment and wages, and we have a chance to return to a normal market economy,” he says.
A more surprising legacy for this “humble civil servant” is that he became an internet star after Japanese social media users celebrated his ability to surprise financial markets with a series of AI-generated dance videos.
