I can see how this game is "hard", but not the difficulty
The game itself is fun with it's usual minor problem solving, puzzle tasks and kill this set of enemies for an item. But for the game to have a reputation of being "hard", I think could have been misplaced. Because all of these tasks were rather easy, a little challenging. But it was like clock work. Not really "hard" at it's core.
Now where I would place the "hard" part? It's the questionable/sloppy camera and controls. Especially the unwanted delayed button response when the action gets pretty intense. Or when Ryu wants to do something else when you want him to complete one task. Like jump across a gap, or walk up a wall. Instead, Ryu would rather run across another wall or go left instead of right. Fighting with "a camera that hates you".
This game would be a lot easier if these problems didn't exist in this game. What makes it hard, are indeed the short comings and not the game's enemies or the stages. I hope the next Ninja Gaiden doesn't have the same problems.
It was a fun game. But it was frustrating none the less. But I have, completed similar in game tasks in the likes of God Of War for example. So it was nothing "new" for me.
/end rant