So good to find the original here too. Both European and western abominations (called respectively Blue Shadow and Shadow of the Ninja) have been simplified by cutting the energy of some of the enemies in half, making them a walk in the park, especially for somebody experienced with the Japanese original.
Completing this game for the 1st time was such a big accomplishment for me in my childhood. It took me more than a dozen attempts to familiarise myself with the bosses and their attack patterns. The final boss was a pain to beat!
One of my favorite nes game from the childhood. That the gamemechanic, graphicdesign, and the amazing soundtracks and effects. Used tobplay with my Brother when we was child. Just like the contra 6 and turtles, nekketsu games.
I remember that holding the attack button for more than 5 seconds (cmiiw) gives you a special attack (regardless of the weapon). the character will stand still and summon a lightning bolt to strike the nearest opponent, at the cost of some health bars. more damage than the usual attack, but - besides sacrificing your own health, it also makes your character vulnerable to attacks during the process. again, cmiiw.