The verb shinobu (忍ぶ) actually means to conceal oneself or to endure. The combination of this root kanji, 忍, with 者, meaning person, creates 忍者—which is synonymous with shinobi-no-mono, but is read "ninja."

Ninja were assassins, mercenaries and experts of espionage who specialized in unconventional warfare. They were covert secret agents who did the jobs that were deemed too dishonorable for the elite samurai.

The Sengoku Period (roughly 1467-1590) was the golden age of ninja in Japan, with Iga in Mie Prefecture and Koga in Shiga Prefecture emerging as the bastions of two key schools of these shadow warriors.

The Iga ninja originated in Iga Province in the area around the towns of Iga and Ueno in Mie Prefecture. The Iga ninja trained in ninjutsu (the art of stealth) in the local mountains and forests, honing their secret art and skills over many centuries. These ninja were trained in the arts of disguise, escape, concealment, explosives, poison, unarmed combat and a multitude of weaponry. The most famous of the Iga ninja was undoubtedly Hattori Hanzo, who saved the life of Tokugawa Ieyasu. When Ieyasu became shogun in 1603, he employed the Iga ninja as guards for Edo Castle (now part of the Imperial Palace in Tokyo) as well as to supply him with intelligence like modern-day spies.

You can discover many of the secrets of the Iga-ryu Ninja Museum in Iga City. It offers visitors a glimpse into the life of ninja and a peek at some of their skills. You can watch a live ninja show, check out a real ninja house complete with revolving walls, fake hallways, hidden compartments and trap doors, admire the ingenuity of ninja weaponry, and even walk on water with the clever use of foot rafts.

Rivaling the Iga ninja were the Koga clan in Shiga Prefecture. Although not as well known, they were said to have used both stealth and deception to mask their true size and power. The Koka region (the ninja tend to be rendered in English as Koga, while the region is Koka) was strategically important, situated on the ancient Tokaido Road, the main route from Kyoto to Edo (modern-day Tokyo). The Koka area was said to have been filled with hidden ninja villages deep in the mountains.

You can explore one of these secret villages and enjoy the hidden world of ninja at the Koka Ninja Village (Koka-no-Sato Ninja Mura). Like taking a step back into the golden age of ninja, this village contains an impressive display of ninja weaponry and historical artifacts, as well as a ninja house with traps doors, false walls and hidden rooms. There's also a "shuriken dojo" where you can try your hand at throwing the famous ninja throwing stars.