[2][3] Throughout Chikayasu's life, he led many an army throughout his older brother Motochika's campaigns in Shikoku and contributing to the expansion of the domain of the Chōsokabe clan.

In 1585, with his brother Chōsokabe Motochika, Chikayasu fought in the Invasion of Shikoku against Hideyoshi's forces.

In 1587, Chikayasu participated in the Toyotomi Hideyoshi Kyushu Campaign against Shimazu clan.

In 1592, Chikayasu participated in the First Hideyoshi's invasions of Korea, along with his brother Chōsokabe Motochika.

Chikayasu died of illness in Nagato province en route to join the Korean Campaign in 1593.