In any level where you can get burned, like in the level with the lasers, kill the last enemy in a tate. In the animation, your character will continue to burn dispite the limited time like that.
Other sites say to get Joe Musashi you need to collect 88 clan coins and beat 80 missions.First of all there is only 86 six clan coins.All you have to do is beat 80 missions.Joe Musashi is the slowest and the weakest but he can use unlimited shuriken and has good 3 good finishers when you kill 4 or more enemies.
Finish the game under normal or hard difficulties. A different alternate costume will be unlocked under each setting.
Collect all 88 Secret Clan Coins in the game.
Finish the game under the easy difficulty.
Insert a memory card with a saved completed game from Shinobi. Now Finish the game under normal difficulty.
Finish a total of eighty eight missions in the game and collect the Secret Clan Coins.