In 1564 Niino Chikanori, a retainer of Ii clan, led a siege to Hikuma castle to prove Naotora's loyalty to Imagawa Ujizane, Otazu and Tsurutatsu fought to defend the castle and Chikanori was killed. Naotora was presumed to have difficulty securing clan leadership because of the innumerable resistances from the Imagawa clan retainers, so she anonymously seeks support from other clans. After numerous threats from Imagawa retainers to Ii, Naotora finally allies with Ieyasu and actively participates in the achievements of the Matsudaira clan in Totomi and Mikawa Province.[4]