Suntory Holdings Ltd.'s recent deal to buy Beam Inc. of the United States is the latest indication that once reputedly risk-averse Japanese firms are becoming more aggressive in expanding overseas operations through mergers and acquisitions (M&As).

One reason for this aggressiveness is the shrinking prospects in the domestic market, where demand is forecast to decline with the falling birthrate and the graying of the population.

In the alcohol beverage sector, for example, shipments of beer and beer-like drinks in Japan fell for the ninth consecutive year in 2013. For Suntory, the Osaka-based whiskey and beer maker, the $16 billion deal to buy the Illinois-based liquor maker of such brands as Jim Beam, Maker's Mark and Canadian Club gives it greater exposure to the profitable spirits market in North America.