Born in 1504 as the eldest son of Chosokabe Kanetsugu, a provincial lord of Tosa. His childhood name was Sennomaru. In 1509, when his father Kanetsugu was defeated and killed by Motoyama Shigemune's forces at Oko Castle, the six-year-old Kunichika fled with his retainers to Nakamura in the Hata estate, taking refuge under the protection of the Tosa Ichijo clan. In 1518, through the mediation of Ichijo Fusaie, he recovered his ancestral lands of Emura and Hatsueda and restored the Chosokabe house as lord of Oko Castle. He later took the character 'Kuni' from Hosokawa Takakuni's name to style himself Kunichika, and went on to subdue neighboring provincial lords one by one. From 1547 onward he destroyed Tenjiku Magojuro of Otsu Castle, Shimoda Suruga-no-kami of Shimoda Castle, and Yamada Motoyoshi of Kuzume Castle through both stratagem and force, expanding his power across southern Nagaoka District into Kami District. In May 1560, he captured Nagahama Castle from his archrival, the Motoyama clan, and repelled Motoyama Shigetoki's attempt to retake it — clearing the path toward the unification of Tosa. He fell ill and died soon after, on June 15 of that year, at age 57. His heir, Motochika, would go on to fulfill the family's long-cherished ambition of unifying all of Shikoku atop the foundation his father had built.

A man of unbreakable resolve who rebuilt his clan from the ashes of exile after losing his father at age six. A patient, methodical ruler who steadily expanded his domain through a shrewd blend of stratagem and force. Often overshadowed by his son Motochika's later exploits, historians credit Kunichika with laying the true foundation for the eventual unification of Shikoku.

The ruins of the castles Kunichika conquered — including Kuzume and Shimoda — are preserved today as historic sites in Kami and Nankoku cities. The unification of Tosa, carried from father to son across Kunichika and Motochika, remains celebrated in Kochi Prefecture as a classic example of Sengoku-era gekokujo, in which provincial lords rose from adversity to power.