Japan's biggest trading houses are calling 2015 a pivotal year for the world's third-largest economy as cheap oil, easy money and a weaker yen promise to boost growth.

Twenty-five years on from the bursting of the bubble economy, which brought decades of deflation, the nation is at a turning point with potential for "painful improvement" in the areas of employment, agriculture and health, Marubeni Corp. Chief Executive Officer Fumiya Kokubu said in a New Year's greeting to staff, posted on the trading house's website.

A confluence of factors gives Japan a unique advantage, according to Mitsubishi Corp., the nation's biggest trader.