Ninja Gaiden II - Now run back to the room that had lasers blocking your way. Go through that door. Right after you go through, there will be a door on your left that has a Muramasa shop in it and a save point.

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Now run back to the room that had lasers blocking your way. Go through that door. Right after you go through, there will be a door on your left that has a Muramasa shop in it and a save point.