Infinity Blade. Over there it'll be called Infinity Blade X for Mobage, and promises to offer multiplayer and co-op features through DeNA's immensely popular Mobage network -- the game will be free to play and supported by the sale of virtual goods.
Infinity Blade, which is considered a "premium" title everywhere else but Japan (see: it costs more than a buck), was just recently updated with head-to-head multiplayer and survival modes. The game's latest milestone saw it surpass $10 million in sales.
Infinity Blade X for Mobage is scheduled to launch in Japan sometime this fall.