At heart, it's a mindless hack-and-slash where you just mash X to make a girl in a bikini or schoolgirl uniform slice zombies into little pieces. But there's a little bit of depth, through the multiple characters and combos that you'll discover. There's one enemy that requires a specific combo to take down, so at the very least, you have to pay attention.
But my favorite feature is probably the mid-game save. You can quit out of the game at any moment, and it'll save your progress and let you pick up from that point later on. That's extremely useful in Survival Mode, where I spent a lot of time earning experience.
Oh, and you have to constantly clean off your sword--too more gore on it and it'll lose its edge and get stuck in zombies. Seriously. I just wish the lock-on was more useful outside of a one-on-one fight--good luck locking on to that big boss when he's surrounded by a few dozen zombies--and that the manual was a bit more detailed.
The move that can take down an otherwise seemingly invincible foe? Not in the manual--I learned of it via a tip that popped up after I died in Survival. And since it involves such specific timing with button presses and moving the analog stick forward--you're literally ripping his heart out--I don't think I would have figured it out myself.