Ninja, while possessing a "magic" skill, are not actual practitioners of magic, per se. They have made use of weapons that can be easily concealed or disguised as common tools. Through intense training they become familiar with these tools, allowing the simplest rope or needle to be used as a deadly weapon. The training and use of these specialized tools is called Ninjutsu (lit. 'the art of stealth'), and a ninja will use them all to defeat his foes.
A category of "spells" used by Ninja. Ninjutsu is used to enfeeble or deal damage to enemies, or buff the caster.
The higher your Ninjutsu Skill is, the more effective your "spells" will be.