Ei Hisabue served as a bushō during the Azuchi-Momoyama period. He was a retainer of the Shimazu clan and served as the eighth head of the Ei clan. He had the common name of Yasaburō.
The Ei clan were an illegitimate branch of the Kimotsuki family. The clan was founded by the son of Kimotsuki Kanemoto (the eleventh head of the Kimotsuki clan) named Kanemasa who adopted the surname of Ei.
In 1583, Hisabue was born as the eldest son and designated heir of Ei Hisatora. In 1587, Hisatora died when Hisabue was five years old. Prior to the birth of Hisabue, Hisatora had promised to adopt the son of Ijūin Tadamune named Senjumaru, but, following the birth of Hisabue, this plan was scrapped. Tadamune complained to his lord, Shimazu Yoshihisa, whereupon, after the death of Hisatora, he was offered landholdings in Ei, Ibusuki, and Yamagawa.
In 1588, Hisabue was granted thirty villages in Taniyama as compensation for his service. In 1593, he was further awarded Nishimata in Ijūin.
In 1597, Hisabue served in the Keichō Campaign and, when crossing to the Korean Peninsula, was promised by Shimazu Yoshihiro that upon his safe return to Japan, the land in Ei would be returned to him, but, the following year, he died of illness in Korea. He was sixteen years old.
The family name was carried on by the fifth son of Shimazu Yoshitora named Shimazu Tadatomi, later known as Ei Hisahide and then as Irikiin Shigetaka.