Lifespan: Bunmei 15 (1483) to 2/28 of Eiroku 9 (1566)
Rank: bushō, daimyō
Title: Master of the Office of Palace Repairs
Bakufu: Muromachi – Military Governor of Hizen
Father: Arima Hisaaki
Siblings: Haruzumi, Saigō Sumihisa
Wife: [Formal] Daughter of Ōmura Sumikore
Children: Yoshisada, Ōmura Sumitada, Chijiwa Naokazu, Matsura Sakō, Shiki Morotsune
Arima Haruzumi served as a bushō and daimyō during the Sengoku period. Haruzumi was the head of the Hizen-Arima clan. He served as the lord of Hinoe Castle in Hizen Province in northwest Kyūshū.
In 1483, Haruzumi was born as the son of Arima Hisaaki.
Haruzumi further expanded the power of the clan that had grown since the era of Haruzumi’s grandfather, Arima Takazumi. Centered upon the Takaki District of Hizen, Haruzumi garnered control of the entire Shimabara Peninsula, monopolizing marine trade, and ushering in the era of peak prosperity for the Hizen-Arima clan. Ashikaga Yoshiharu, the twelfth shōgun of the Muromachi bakufu, recognized the power of the clan. In 1539, Haruzumi received one of the characters in his name from Yoshiharu. This followed the tradition of his father, Hisaaki, who received one of the characters in his name from the ninth shōgun, Ashikaga Yoshihisa. Haruzumi was also conferred the title of Master of the Office of Palace Repairs. At this time, he returned the honor by donating a sword, a horse, and gold pieces to the Ashikaga shōgun family.
In 1546, Haruzumi toppled the base of Ryūzōji Iekane at Mizugae Castle, but, two months later, was subject to a counterattack by Iekane and the castle was retaken by the Ryūzōji. Thereafter, Haruzumi sent his second son, Arima Sumitada to be adopted by the Ōmura clan. He then sent his third son, Chijiwa Naokazu to the Chijiwa clan and his fourth son, Hata Mori, to the Hata clan for adoption with the aim of strengthening his authority in Hizen.
In 1550, after Portuguese vessels entered his territorial waters, the Arima clan benefited from trade with the foreigners from Portugal and Spain referred to as the southern barbarians. At the same time, however, the Christian religion also began to spread in parts of Japan. Haruzumi was said to have hated the Christian religion and violently suppressed them.
In 1552, he transferred headship of the clan to his eldest son, Arima Yoshisada, and retired to lead a quiet life. At this time, however, the invasion of Hizen by Ōtomo Yoshishige (Sōrin) and Ryūzōji Takanobu intensified and, around the time that Haruzumi died, the power of the Hizen-Arima clan had precipitously declined.
In 1566, Haruzumi died at the age of eighty-four.