I discovered something today on Tenchu Z and though I would share it with you guys, If anyone is having problems with the 3 boss fights (Ninja guy at the docks, final guy on last mission & ninja guy again after that fight) I found a way you can win easy.
So basically what you do is on the dock level with the first boss fight agaist the ninja, is run off the boat and make sure he is following you, just run to dock and then keep meleeing him towards to edge of the dock aka into the water, after a couple of melee hits and if u can face him with his back to water he should fall in and boo end of fight. So if you were having problems fighting him on say hard theres ur easy way
well onto the last 2 bosses, this one can be a bit more testing then last one, what u need to do is climb out of the window when u engage combat with the boss, You want to climb out of east window if you are facing the main doorway into the castle. Once you get out of the window he should try to follow you, once he is out there with you, make him face his back to edge of the roof and keep meleeing him intil he falls off onto the lower roof. Jump down and repeat what you did above, he should fall to the ground level so Jump down and make sure u hit RB for soft landing so u dont smash into the floor. Once u land make him face the edge of cliff type thing that has a river below, now just keep meleeing him intil he falls and woola one dead boss
With the 2nd fight with the ninja right after the above boss, just run all the way back up to the top level of the castle and repeat what you did to the last guy.
Some people might find this harder then fighting him like ur ment to but for me this was an easier way. So hope this helps people who are stuck or having problems fighting these guys.