Born in 1542 in Mikawa Province as the son of Hattori Hanzo Yasunaga, who hailed from Iga. His real name was Masanari. He fought his first battle at 16 and went on to serve Tokugawa Ieyasu, earning fame as a spearman and the fearsome epithet 'Demon Hanzo.' His greatest achievement came in 1582, right after the Honno-ji Incident, when he mobilized Iga and Koga ninja to escort Ieyasu safely from Sakai to Mikawa through the perilous Iga-goe crossing. For this service he was given command of 200 Iga doshin and assigned to guard the western gate of Edo Castle—later named 'Hanzo-mon' (Hanzo's Gate), which still stands as a gate of the Imperial Palace. He died on November 4, 1596, at age 55.

A straightforward warrior of unwavering loyalty. Though known as a ninja leader, he himself was a samurai in armor who wielded a spear. Taciturn and composed, he risked his life without hesitation in his lord's hour of need.

Globally famous as the archetypal ninja for rallying the Iga shinobi to protect Ieyasu. Hanzo-mon Gate remains a Tokyo landmark, and the Hanzomon subway line bears his name.