桶狹間之戰
Ii Naomasa was born in Hōda Village of Tōtōmi Province. His childhood name was Toramatsu (虎松) later Manchiyo (万千代). His family, like the Tokugawa, had originally been retainers of the Imagawa clan, but following the death of the clan's leader, Imagawa Yoshimoto, in the Battle of Okehazama (1560), confusion and general chaos ensued. Naomasa's father, Ii Naochika, was falsely convicted of treason by Yoshimoto's paranoid successor, Imagawa Ujizane, and was subsequently killed.