But the mask began to slip last year when Abe decided to delay a sales tax hike, making Japan's primary fiscal goal harder to achieve.
"The honeymoon days are over," said Izuru Kato, chief economist at Totan Research. "Kuroda must be frustrated over a lack of progress in structural reform and fiscal consolidation."
A former finance ministry bureaucrat, Kuroda feels Japan cannot afford to delay tax hikes and spending cuts given its dire fiscal state, while Abe prefers to focus more on boosting growth to raise tax revenues.
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Last month a key policy panel run by Abe's right-hand man, Economics Minister Akira Amari, began debating proposals that could water down Japan's fiscal target of returning to a primary budget surplus, excluding debt servicing costs and income from bond sales, in fiscal 2020.
Abe has not resiled from that target, but the panel is laying the ground for him to add other goals that give him more wiggle-room on spending, government officials say.
Breach of etiquette
His favorite idea, floated at the panel, is to add a goal on the ratio of debt to GDP. This ratio falls without deep spending cuts, as long as the BOJ maintains both low interest rates and solid economic growth with its massive stimulus.
Defying central bank etiquette, Kuroda spoke against the proposals at a panel meeting on Feb. 12 in front of Abe.
He returned to the theme two weeks later, despite raised eyebrows in government.
"Achieving the primary balance target is just a first step. Only through this would Japan think about gradually reducing the debt-to-GDP ratio," he told reporters.
Behind his concern is that Japan's huge public debt could lead to cuts in its sovereign debt ratings, which in turn would hurt Japanese banks with huge bond holdings.
Delays in fiscal reform are also likely to leave the BOJ with a bloated balance sheet, already equal to 60 percent of GDP, for longer than it wants.