Lesser Ninja is an enemy family in Final Fantasy Dimensions. They are fully clothed humans who fight with a single sword.
They are related to the Ninja enemy family who are stronger.
The orange-colored Lesser Ninja is used for Ariari, an enemy from the Developers' Room. The enemy sprites used for the developers were not created specifically for the developers and they just reuse other sprites, so the orange ninja may have been used for another enemy only available in the original phone version, or an enemy that never appeared in the game.