Not much to add to the good reviews. Indeed, Okami is based on the evolution of zelda system (one acquires a skill, one progresses etc ...) but offers a less smooth universe (politically correct what ...) than the latter. The combat system is much more developed, in short, they are inspired by pushing the plug further than the original! It is also much more beautiful and it is an incredible injustice that this game did not work, forcing the studio to close.
The Zelda killer (and it is the only one) I tell you!