Masanari Hattori rose to command the Edo Castle guards for Tokugawa Ieyasu after the Battle of Sekigahara. Leading a band of Iga ninja, his leadership faced significant challenges when these forces rebelled against his treatment, resulting in profound humiliation within the Tokugawa hierarchy.

During the pursuit of two fleeing rebels, he committed a killing later deemed a case of mistaken identity, leading directly to his removal as guard captain. Driven to restore his reputation and family name, he later led a contingent of 60 Iga ninja into the Siege of Osaka. His involvement culminated in his death during the second siege.

Within the anime *Shinshaku Sengoku Eiyū Densetsu - Sanada Jū Yūshi The Animation*, Masanari Hattori appears during the Battle of Sekigahara segment, his role reflecting his historical involvement in the conflict between the Eastern and Western armies.