Ninjutsu

Ninjutsu is an art that was introduced to the Other World by a Wanderer known as Hanzo.

Background
Hanzo introduced this art nearly six hundred years ago when he arrived in the Other World. While under the employ of the Revlon Empire, Hanzo took six beastmen as his disciples and gifted them the ability to use ninjutsu. Together he formed the empire's most elite spy unit. However after the Empire's nobles began to conspire against him, Hanzo manipulated the events of the empire and caused it to split in half under a civil war. In the confusion, Hanzo escaped the nation with his followers and several beastmen slaves that would form the Jinshin Clan. Hanzo's teachings of ninjutsu would become his legacy to the beastmen who renamed themselves the mountain people and continue to fight against human oppression.

Mechanics
Ninjutsu while appearing to be a different kind of magic, is actually a branch of spirit magic. Normally besides elves, other races are not able to utilize spirit magic at least not with the degree of skill of the elves as it involves communication with the spirits to performs certain feats of magic.

Normally beastmen affinity for magic is quite low compared to other races. The ninjutsu that the Jinshin Clan practices is achieve through powerful magical artifacts from their founder, the pledge spirit crystals. These items contain spirits which users can make contract with.

Abilities
The spirits using the users as hosts then allow for the use of impressive forms of spirit magic. This enables the users of these crystals to directly convert their own mana into magic, akin to spirit animals.

Unlike elves who transfer mana within themselves to the spirit they contracted which in turned that into magic based on their contracts.

Trivia

 * Ninjutsu while powerful technique is still limited as it requires a pledge spirit crystal, of which only ten are in existence.