I played this around 5 years ago, and this is how a stealth ninja game should be.
You're not supposed to be a one-man army pseudo-ninja wielding magical power and stuffs, you use your brain and skills to get past the enemy.
You don't force your way in, you slip between nooks and crannies, slide beneath the shadows. You engage your enemies in stealth.
Your enemies aren't supposed to be blade-fodder(?), walking dummies for you to massacre freely. They should be real dangers that you must consider in your planning.
You shouldn't be forced to walk only one way to your objective, but instead you should be able to decide how you're going to approach your mission.
Shinobido gives all of that. While the 'blackbox approach' concept has just been popularized recently by mainstream game developers, Shinobido utilized it long before.