Lifespan: 15xx to Bunroku 2 (1593)
Title: Assistant Head of Bureau of Cultural Affairs (informal)
Clan: Arikawa → Ise
Lord: Shimazu Takahisa → Shimazu Yoshihisa → Shimazu Yoshihiro
Father: Arikawa Sadanori
Siblings: Sadamatsu, Sadamasa, Tōgō Shigekatsu
Wife: [Formal] Daughter of Niiro Tadamoto
Children: Sadanari, Sadamasa, daughter (wife of Kamata Masatomi)
Arikawa Sadamasa served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a retainer of the Shimazu clan and his formal wife was the daughter of Niiro Tadamoto.
The Arikawa clan were purported descendants of the Ike clan from the branch of Taira no Yorimori of the Kanmu-Taira family. The clan’s presence in Satsuma Province began in the era when Arikawa Sadayo served Shimazu Takahisa. Initially, the clan adopted the name of Arikawa, but the Arikawa were minor lords in Ise Province, and hatamoto, or direct retainers, of Tokugawa Ieyasu. Upon permission of a relative named Ise Sadatame, Sadamasa and his older brother, Sadamatsu, adopted the surname of the Ise clan and, together with Sadamatsu, he became a founder of the Ise clan in Satsuma Province.
In 1564, Sadamasa served Shimazu Yoshihiro, entering Iino in Masakiin and became a chief retainer. On 1/20 of Eiroku 11 (1568), Sadamasa participated for Yoshihiro in an attack on Ōkuchi Castle. On 5/4 of Genki 3 (1572), during the Battle of Kizakibaru, Sadamasa remained behind with twenty soldiers to guard Iino Castle while Yoshihiro was away on deployment. In 1573, after the Hyūga-Itō clan experienced a loss of power owing to the outcome of the battle, retainers of the Itō including Mera Norishige (lord of Suki Castle), Hidaki Saburō Hyōei-no-jō (lord of Nasaki Castle) and Nakayama Kazue submitted written pledges to Sadamasa, expressing their intention to switch their loyalties to the Shimazu clan.
In 1581, Sadamasa deployed for an attack on Minamata and, in 1582, after entering Yatsushiro, regularly followed Yoshihiro in battle. Around this time, he was appointed to serve as the steward of Iino. In 1586, he also accompanied Yoshihiro into Bungo Province.
In 1592, Sadamasa obeyed Yoshihiro and participated in the Bunroku Campaign but, in 1593, he died of illness on the Korean Peninsula.