Lifespan: Eishō 10 (1513) (or Meiō 4 (1495)) to 1/16 of Eiroku 8 (1565)
Rank: bushō, daimyō
Title: Junior Fifth Rank (Lower), Master of the Eastern Capital Office
Bakufu: Muromachi – Military Governor of Harima, Bizen, Mimasaka
Lord: Ashikaga Yoshiharu
Father: Akamatsu Yoshimura
Siblings: Harumasa, Masamoto
Children: Yoshisuke, Noriie, daughter (wife of Akamatsu Masahide), daughter (wife of Miki Michiaki), Masasuke
Akamatsu Harumasa served as a bushō and daimyō during the Sengoku period. Harumasa was the eleventh head of the Akamatsu clan. He served as the military governor of Harima, Bizen, and Mimasaka provinces. Harumasa was the lord of Okishio Castle in Harima.
His childhood name was Saimatsumaru and his common name was Jirō. His first name was Masamura and then he adopted the name of Masasuke. In this profile, he is referred to as Harumasa. He held the title of Junior Fifth Rank (Lower) and Master of the Eastern Capital Office. The title of Junior Fifth Rank (Lower) was often conferred upon those persons who provided donations to support the construction and operation of facilities for the Imperial Court and temples and shrines under their dominion. With Kyōto as the seat of power for the central authorities, the Master of the Eastern Capital Office (the highest of the four official positions of the ritsuryō system of governance) was appointed to govern the east of Kyōto (to the left of the south-facing throne).
In 1513, Harumasa was born as the son of Akamatsu Yoshimura. There is another theory that he was born in 1495.
In 1520, Harumasa inherited the headship of the clan at the age of eight after his father, Yoshimura lost in a conflict against the Uragami clan, the deputy military governors, and was forced into retirement. Thereafter, Yoshimura failed in a counterattack against Uragami Muramune, the deputy military governor of Bizen, and, in the ninth month of 1521, was killed. To resist an invasion by the Yamana clan, Harumasa temporarily joined forces with Muramune, but, after the threat from the Yamana clan subsided, fell into conflict again with the Uragami. For a period, Harumasa was ousted from his base at Okishio Castle and was compelled to take refuge at Shinjōyama Castle in Mimasaka.
In 1531, Uragami Muramune backed Hosokawa Takakuni, the deputy shōgun, in a conflict with Hosokawa Harumoto, the eldest son of Hosokawa Sumimoto. This amounted to the final chapter in the Conflict between the Hosokawa. After Muramune invaded Settsu Province, Harumasa participated by serving in the rear guard, but, in fact, Harumasa secretly sent hostages to Ashikaga Yoshitsuna, the Sakai kubō, based on a promise to betray the Uragami clan. On 6/4 of Kyōroku 4 (1531), while positioned at the Kannō Temple, Harumasa colluded with those on the side of Harumoto and attacked the forces of Takakuni and Muramune from behind. Meanwhile, Harumoto’s forces joined to form a pincer attack, decimating the forces of Takakuni and Muramune. Muramune died in battle while Takakuni was forced to take his own life. This event is known as the Collapse at Daimotsu.
Consequently, while Harumasa regained some of his authority, a conflict persisted between Muramune’s son, Uragami Masamune, and Uragami Munekage. In the eighth month of 1534, a violent conflict erupted on Mount Asahi. Owing to an invasion by Amago Akihisa (later known as Amago Haruhisa) of Izumo Province in the twelfth month of 1537, the Uragami siblings who had been in conflict were obedient, but Harumasa’s territory turned into chaos, and Uno Murayori of Shisō betrayed Harumasa. In the seventh month of 1538, Harumasa turned to the Kajiwara clan at Takasago Castle, but incurred an attack by Kodera Norimoto and Akashi Masakaze after their betrayal and fled to Tamura Noto-no-kami for protection in Kōge in Awaji Province. On 4/8 of Tenbun 8 (1538), Harumasa garnered support from the Awa-Hosokawa clan, landed in Akashi and attacked Edayoshi Castle, but a rumor circulated that the Bessho clan at Miki Castle (who had resisted the Amago forces to the end) were colluding with them so, on 11/25, he fled for safety to the Kaie Temple in Sakai.
In the wake of a failed expedition to Aki Province by the Amago clan from 1540 to 1541, an event known as the Siege of Yoshida-Kōriyama Castle, the Amago army withdrew from Harima. While Harumasa avoided a crisis in his territory, this did not prevent the loss of authority of the Akamatsu clan. Around this time, Harumasa received one of the characters from the name of Ashikaga Yoshiharu and adopted the name of Harumasa.
In 1552, after Amago Haruhisa was appointed by the Muromachi bakufu to serve as the military governor of Bizen and Mimasaka, Harumasa lost his authority as the military governor of these provinces. Meanwhile, his authority in Harima was eroded by the Uragami clan. In the eighth month of 1558, Kodera Masamoto backed Harumasa’s eldest son, Akamatsu Yoshisuke, in a coup d’état, whereupon Harumasa fled to the base of his son-in-law, Akamatsu Masahide, at Tatsuno Castle. This ended the Akamatsu family line of succession and the Akamatsu fell from their position as shugo damiyō of the landlord class to that of a local power. Thereafter, under the protection of Masahide, Harumasa moved his base of power to northern Harima and to Mimasaka, allying with the Mōri clan and local landowners including the Sagayama, the Hirodo, and the Toyofuku clans to govern their territories. He died on 1/16 of Eiroku 8 (1565).
His grave is on the remains of the Shōan Temple in the city of Himeji.