As fun as it was seeing zombies in a Yakuza game, even more fun is seeing pirates and detectives face off against those zombies. You'll get that chance if you download some of the Yakuza Of the End content Sega is offering as free download content.
Here you can the Detective Akiyama, Pirate Majima, I-Don't-Know-What-Fuck-That-Costume-Is Goda, and American Maniac Kiryu.
