The slide in the yen has turned Mazda Motor Corp.'s biggest weakness into its biggest strength. All Japan's most export-dependent automaker has to do now is sell more cars.

Japan's fifth-largest car company has the wind of the yen's 16 percent descent in the past six months in its sails. Shares have tripled to their highest level since 2008 as more-profitable exports and cost reductions steer Mazda toward its first annual profit in five years.

Despite Mazda's status as the top performer on Japan's benchmark stock index over the past six months, the Hiroshima-based carmaker needs to make a hit out of a new version of the Mazda3, its top seller, due this fiscal year, to prove it doesn't require a weak yen to compete against its bigger rivals.