We know Vanillaware from its RPG titles like Odin Sphere, but while Muramasa shares the same lavish 2D look, it differs sharply in gameplay style -- this is a pure action game similar to something like Legend of Kage. First you choose one of two characters, princess Momohime or ninja Kisuke (each have their own divergent story), and then a difficulty level, "Muso" (easier) or "Shura" (hard). Then you run, jump, and slash monsters. It's pretty simple!
Gameplay takes place in small, self-contained areas, like the "rooms" of a Metroid or Castlevania game, but more linear. There was only one exit to each area we played. Occasionally there will be a "village" area where you can talk to people and look for items, but most areas are for fightin'. When monsters appear, you can't progress until you've defeated them. The Wiimote's A button controls your sword in extremely juggle-friendly combat. Mashing A starts some fairly chaotic combos, which launch enemies high in the air. Holding a direction on the analog stick will make you move that direction as you attack, even in the air, so once you get airborne, you can juggle enemies all over the place. Every swing of the sword causes total insanity on the screen.
Keeping you from rapid-firing A through the game is the sword "soul" system. You have to pick up dropped items from enemies to restore your sword's "soul," otherwise it will break. You can also prevent this by swapping between the available weapons with the C button. Momohime has three swords of different sizes in her inventory, and swords restore their soul when not in use.
This is most important in boss battles. At the end of the level, I faced the cyclops creature seen in early screenshots. He mostly just walked back and forth and occasionally belly-flopped me, but this was difficult enough due to the sword restriction. We wore out sword after sword on him, and his health just kept regenerating. Finally, I ran out of time and had to surrender the controller in shameful defeat.
There simply aren't any games like this anymore, on the Wii or anywhere else. But at the same time, while sidescrolling action games are inherently old-school, the graphics couldn't be done on any previous generation. The gorgeous 2D graphics are definitely improved over the look of Odin Sphere -- sharper, more colorful, and with much better animation.