Naomasa Ii was an officer under Ieyasu Tokugawa, and lived from 1561 to 1602. He was born into a turbulent era for the Ii, as they were retainers of the Imagawa clan, who had suffered the catastrophic loss of their daimyo Yoshimoto Imagawa at the Battle of Okehazama in 1560, and the Ii clan's own head, Naomori Ii, was killed in the same battle. Around this same time, Naomasa's father and Naomori's nephew Naochika vied to gain control of the Ii clan by marrying his cousin and Naomori's daughter Naotora Ii.
However, Naochika was betrayed by an Imagawa retainer who falsely charged him with treason. This led to further turbulence until Naotora was declared leader of the Ii clan. Naotora also adopted and raised Naomasa.
Later in life, Naomasa entered the service of Ieyasu Tokugawa, and served him as a faithful officer. He ultimately served as a general at the Battle of Sekigahara in 1600, where he was wounded by gunfire. It is thought that complications from the wound are what ended his life in 1602.