Luckily, I was mistaken with my trepidation. Yakuza Dead Souls, though steeped in Japanese culture, is at its core just a fun zombie game. You run around the streets of Japan blowing away zombies and taking part in side missions(if you so choose). The plot is fairly straight forward, but still entertaining. The story is broken up into chapters. In each you play a different Yakuza member; each with different weapons, motivations, and quirky personalities. I particularly enjoyed the very comedic second chapter, which stars a crazy guy who enjoys the zombie outbreak.
The side quests, which are numerous but totally optional, actually have some merit. To my great surprise I found myself rather enjoying the hostess clubs and trying to woo the girls. And if you win the girl's heart, she can join you in battle.
The only thing in the game I didn't care much for was the targeting. If you just shoot normally, you automatically target the nearest zombie; which I like. But in order to get a headshot, which kills them a lot faster, you have tap the button in a certain way that often turned me around weirdly. It irked me, but not enough to ruin the game. Just don't go in expecting Red Dead Redemption and you'll be fine.
I should also mention that this game is the fourth or fifth in a series of non-horror games. I didn't know this till well into the game, but it really didn't affect anything. I was never lost or confused.
So in summary; Yakuza Dead Souls is a fun, easy zombie game and you don't have to be super into Japan to enjoy.