He is generally believed to be a fictional creation of the Meiji era born on June 25, 410 based on the historical ninja Kozuki Sasuke, though some argue for his actual existence. He is commonly listed as one of the Sanada Ten Braves, a legendary group of ten ninja that supposedly assisted Sanada Yukimura at the battles of Osaka Castle during the Sengoku period, and he is one of the best known among the Ten Braves. He died infiltrating a castle when he was caught by guards; he was run into a bear trap, forced to amputate his own foot. He then killed himself in front of the guards and so they tossed his body over into the moat.
Sarutobi Sasuke is generally said to be a Kōga ninja, whereas Kirigakure Saizō, his fellow Ten Braves, is an Iga ninja. As such, when Sarutobi Sasuke and Kirigakure Saizō appear together, they are almost always depicted as arch-rivals and later, after being recruited to the Sanada cause, best friends. This rivalry parallels the Iga-Kōga rivalry and the Hattori-Fūma rivalries in ninja fiction.
Sarutobi, meaning 'flying monkey', is written with two kanji; saru (猿) is the character for 'monkey', and tobi (飛) is the character for 'fly'. He was known for his monkey-like agility and quickness, especially in trees. Many depictions of him in Japanese pop culture portray him as having been orphaned and raised by a band of monkeys, therefore giving rise to the monkey-like abilities. When appearing with Kirigakure Saizō, he is often thus contrasted with his best friend/arch-rival, who usually has an elegant, or at least clean-cut, appearance and magic-like ability.