Lifespan: Kyōroku 2 (1529) to 3/9 of Tenshō 6 (1578)
Clan: Akai → Ogino → Akai
Lord: Akai Iekiyo → Oda Nobunaga
Father: Akai Tokiie
Siblings: Iekiyo, Naomasa, Yukiie, Tokinao, Yamaguchi Naoyuki
Wife: [Formal] Daughter of Hatano Motohide, [Second Wife] Daughter of Konoe Taneie (known as Keikōin)
Akai Naomasa served as the de facto leader of the Akai clan. The Akai were a gōzoku, or a provincial family of means and influence, based in the Hikami District of Tanba Province.
Era of the Ogino clan
Naomasa was born in 1529 as the second son of Akai Tokiie. Under Naomasa’s older brother, Akai Iekiyo, the clan controlled almost all of the Hikami District. Naomasa was adopted by the Ogino clan based on Kuroi Castle in Tanba and was given the Ogino name. In 1554, he slayed his adoptive uncle, Ogino Akikiyo, and seized control of the castle. This incident gave rise to his nickname of Akuemon, or the evil one. Owing to his fierce nature, he was also referred to as the Red Demon of Tanba.
Naomasa wed the daughter of Hatano Motohide as his formal wife, but she later died. He then married as his second wife the daughter of Konoe Taneie, a noble of the Court with the highest-ranking title of kanpaku, who was also the younger sister of Konoe Sakihisa. He had one daughter with her.
In 1557, Naomasa’s older brother, Iekiyo, died as a result of injuries sustained in a battle against Matsunaga Nagayori (later Naitō Munekatsu), a retainer of the Miyoshi clan. Naomasa then became head of the clan at Kuroi Castle and guardian of his young nephew, Akai Tadaie. In 1558, Naomasa expanded his territory by defeating Araki Naomasa of the Amata District. In 1565, he attacked Shiomi Yorikatsu, lord of Yokoyama Castle (known as Fukuchiyama Castle) in Tanba. In a showdown in the Waku neighborhood, Naomasa killed the rival Nagayori, who had earlier killed Naomasa’s older brother.
Battles against the Oda
In the third month of 1570, Naomasa and Tadaie surrendered to Oda Nobunaga and received a territory comprised of three districts in Tanba. In 1571, Naomasa repelled an invasion by Yamana Suketoyo and, in turn, captured Konosumiyama and Takeda castles from the Yamana in northern Tanba. Suketoyo requested support from Nobunaga, leading to an invasion of Tanba by the Oda. In the first month of 1573, a rumor circulated that Naomasa would deploy to Kyōto on behalf of Ashikaga Yoshiaki. Later that year, Yoshiaki sought help from Naomasa. In the seventh month of 1574, Naomasa received a letter from the Takeda criticizing the seizure by Hashiba Hideyoshi of landholdings of the Matsuo Shrine, whereupon Naomasa joined the opposition to Nobunaga. During the period from 1573 to 1575, Naomasa provided refuge for his brother-in-law, Konoe Sakihisa, after Sakihisa fled Kyōto.
In the tenth month of 1575, Oda Nobunaga ordered Akechi Mitsuhide to invade Tanba under the pretext of overthrowing Naomasa. At the time, Naomasa was attacking Takeda Castle, defended by Ōtagaki Terunobu who served Kikkawa Motoharu. Once Mitsuhide took action against Takeda Castle, Naomasa fled to Kuroi Castle. With the benefit of reinforcements from Hatano Hideharu of Yakami Castle, Naomasa prevailed against Mitsuhide in a conflict known as the Battle of Kuroi Castle. Therafter, Tanba was subject to continuing attacks by the Oda who had solidified control of the Kinai Region emanating from the capital of Kyōto. Naomasa and the Akai clan joined closely with the Hatano to fiercely resist the Oda and succeeded multiple times in their attacks against the Oda army led by Mitsuhide. After Naomasa encircled Mitsuhide’s forces in battle, Mitsuhide is said to have believed this was the end.
However, in the third month of 1578, Naomasa died of illness at age fifty. His eldest son, Akai Naoyoshi, was only nine years old at the time, so his uncle, Akai Yukiie, took command. Nevertheless, the Akai clan lost its unifying force and collapsed, hastening the subjugation of Tanba by the Oda.