Harunobu Kasai was born in Miyagi Province in the mid-16th century, and served Harumune Date until his death, and served Masamune Date thereafter. Harunobu Kasai was loyal to the Date clan, and plotted a rebellion in Miyagi Province in 1591 when Masamune's territory and titles were stripped from him following his refusal to participate in the Fall of Odawara. Harunobu Kasai and Yoshitaka Osaki rebelled, causing turmoil in Miyagi Province. That year, Concubine Kai and a large Toyotomi Army arrived to crush the uprising. Concubine Kai killed Harunobu, who attacked her father Ujinaga Narita.