Ii Naochika served as a bushō during the Sengoku period.  He was a retainer of the Imagawa clan and the nineteenth head of the Ii clan, kokujin, or provincial landowners, in Tōtōmi Province.

In 1536, Naochika was born as the son of Ii Naomitsu, a retainer of the Imagawa clan.

In 1544, owing to slander by Ono Masanao, Naochika’s father, Naomitsu, was executed by Imagawa Yoshimoto.  Given the possibility that the youthful Naochika would also become a target for execution, he was taken by retainers and absconded to Iinoya.

His grandfather, Ii Naohira, relied upon a Zen priest introduced to him by the abbot from the Ryōtan Temple and enabled Naochika to safely escape to the Shōgen Temple in the Ina District of Shinano Province in territory controlled by the Takeda clan.  According to one theory, while in Shinano, Naochika, together with a wife from the Shiozawa clan, had a daughter, Takasehime, and son, Ii Yoshinao.

In 1555, after Naochika was able to return to Iinoya, he established a base at Iwaida and wed Okuyama Hiyo, the daughter of Okuyama Tomotoshi.  In 1560, after his older cousin and adoptive father, Ii Naomori, was killed at the Battle of Okehazama, Naochika inherited the headship of the clan.  At the time, kunishū across Tōtōmi rebelled against the Imagawa clan in an event known as the Enshū Discord.  Based on slander by Ono Michiyoshi (the son of Ono Masanao), Naochika was suspected by Imagawa Ujizane of colluding with Matsudaira Motoyasu (later known as Tokugawa Ieyasu).  Through the offices of a relative named Niino Chikanori, while traveling to Sunpu to apologize, on either 12/14 (or 3/2) of Eiroku 5 (1563), Naochika was attacked and murdered by Asahina Yasutomo, a senior retainer of the Imagawa, at the Kake River.  He was twenty-eight years old.

In the background of Naochika’s murder, it is noted that among the members of the Ii clan who governed an area near Mikawa, there was a conflict between one faction who supported the Imagawa and others opposed to the Imagawa.  As a member of the group opposed to the Imagawa, Naochika aligned with Motoyasu while Michiyoshi supported the Imagawa.

For this reason, the Ii clan entered into a temporary period of decline.  The headship of the clan was inherited by Ii Naotora, a landowner in Iinoya – the former fiancé of the daughter of his adoptive father, Ii Naomori.  His lineal heir, Ii Toramatsu, was harbored by the Hōrai Temple and at the age of fifteen served Tokugawa Ieyasu and in lieu of Naotora as the head of the clan.  Later, he became Ii Naomasa, a daimyō counted among the Four Divine Kings of the Tokugawa.  After Tōtōmi came under the control of Ieyasu, Naochika’s innocence was established and Ono Michiyoshi was publicly executed.

There is a scarcity of concrete information regarding his achievements.  There is a legend that when Naochika was fleeing from Tōtōmi, Ukon Jirō attempted to shoot him.  After making a comeback, Naochika then took steps to have him killed.  According to another story, he was skilled at the flute and donated his prized flute to a monk who assisted him to flee from Tōtōmi.

One scholar noted there are no traces of Ii Naochika in materials from his era, and his name first appears in genealogies made in later periods, so there are questions regarding his existence.