In the ninth level, Reclaim the Castle, is a big shorcut which is not supposed to be in the game. Climb to the first roof of the castle and go on the very edge. Make sure you don't fall off. Pull out your grappling hook and aim it straight up and shoot it. If you were close enough to the edge when you did this, your character will grab on just below the spikes. Pull yourself up and pull yourself up again. Walk forward to begin the boss battle. This glitch lets you skip the 20 or so enemies that you normally would have to fight.
Earn 400+ (Grand Master) points for each mission.
Training Mission - Super Shuriken
Mission 1 - Lightfoot Scroll
Mission 2 - Fire-Eater Scroll
Mission 3 - Protection Amulet
Mission 4 - Sleeping Gas
Mission 5 - Ninja Armor
Mission 6 - Shadow Decoy
Mission 7 - Resurrection Leaf
Mission 8 -Chameleion Spell
Mission 9 - Dog Bone
Mission 10 - Decoy Whistle