While there are several styles of "modern ninjutsu", the historicity and lineage of these styles is disputed.
Spying in Japan dates as far back as Prince Shōtoku (572–622). The first open usage of ninjitsu during a military campaign was in the Genpei War, when warriors were chosen to serve as shinobi during a battle. This manuscript goes on to say that during the Kenmu era, Kusunoki Masashige frequently used ninjitsu. According to footnotes in this manuscript, the Genpei War lasted from 1180 to 1185, and the Kenmu Restoration occurred between 1333 and 1336. Ninjitsu was developed by the samurai of the Nanboku-cho period, and further refined by groups of samurai mainly from Kōka and the Iga Province of Japan in later periods.
In Mortal Kombat
It is used as primary fighting style by Cyrax in Mortal Kombat: Deadly Alliance and Armageddon, and by Sektor in Mortal Kombat: Tournament Edition, because of him being a palette swap of Cyrax in that game.
In Mortal Kombat X, one of Scorpion's character variations is Ninjutsu. This variation focuses on utilizing Scorpion's ninjitsu training over his demonic powers, which involves the use of his dual swords.
Ninjitsu is one of the only fighting styles made up of several other fighting styles, like hand to hand combat and illusionary combat.