Zynga, the maker of FarmVille and other popular social games, is preparing for an alliance with Japan’s Softbank investment firm as a way to break into the fast -growing Japanese market, VentureBeat has learned. Japan is seeing significant growth in social gaming, even the U.S. shows signs of a slowdown. Mark Pincus, the CEO of Zynga, had backing from a Softbank affiliate for one of his previous c