Lifespan: Tenbun 7 (1538) to 10/5 of Tenshō 14 (1586)
Title: Governor of Hōki
Lord: Hosokawa Harumoto (through affiliation with the Miyoshi) → Oda Nobunaga
Father: Shiokawa Kunimitsu
Mother: Ryūshōin (daughter of Itami Chikanaga)
Siblings: Unsōken, Nagamitsu, Torako (wife of Shiokawa Yorimune)
Wife: Daughter of Ashikaga Yoshiteru (?)
Children: Aizō, Suzu (consort of Oda Nobutada), daughter (widow of Ikeda Motosuke)
Adopted Children: Tatsuchiyo
Shiokawa Nagamitsu served as a bushō during the Sengoku and Azuchi-Momoyama periods. Itami Chikaoki was a cousin of Nagamitsu.
In 1538, Nagamitsu was born as the son of Shiokawa Kunimitsu, a kokujin, or provincial landowner, from Settsu. His mother, Ryūshōin, was the second wife of Kunimitsu from the Itami clan.
Initially, Nagamitsu associated with the Miyoshi clan, but, around the time that Oda Nobunaga marched upon Kyōto in the autumn of 1568, Nagamitsu submitted to his command and received recognition of his rights to a fief of 20,000 koku. In the eighth month of the same year, he joined in the siege of Noda-Fukushima. In 1573, after conflict erupted between Nobunaga and Ashikaga Yoshiaki (the fifteenth shōgun of the Muromachi bakufu), one account notes that he joined with Matsunaga Hisahide who supported Yoshiaki, indicating that Nagamitsu was opposed to Nobunaga. In 1575, Nagamitsu visited Nobunaga at the Shōkoku Temple in Kyōto and received a horse, so it is surmised that, before long, he had surrendered to Nobunaga. Moreover, around this time, he affiliated with Araki Murashige, the military governor of Settsu Province.
In 1578, after Murashige launched a rebellion against Nobunaga, Nagamitsu participated in the Siege of Arioka Castle, which finally ended in the tenth month of 1579 after Murashige slipped away with a small group under cover of darkness to Amagasaki Castle. In 1580, Nagamitsu joined another attempt to force the surrender of Murashige at the Siege of Hanakuma Castle, but, once again, Murashige evaded capture, finding refuge with the Mōri clan in Ōmi Province.
On 9/17 of Tenshō 8 (1580), Nagamitsu lured Nose Yorimichi from a neighboring gōzoku or wealthy family, to Tada and had him killed. This owed to the failure of the Nose to respond to a summons from Nobunaga. In the eighth month of 1581, orders were given to Nagamitsu, along with other groups from Settsu and Ikeda Tsuneoki, to deploy to the western region as yoriki, or security officers for Akechi Mitsuhide. In the ninth month, he dispatched reinforcements for an attack against Tottori Castle. In the fifth month of 1582, another order came to invade the western provinces. This was halted, however, after the coup d’état led by Mitsuhide against Nobunaga known as the Honnō Temple Incident on 6/2 of Tenshō 10 (1582).
Nagamitsu sent a letter to Hashiba Hideyoshi, advising him in regard to the situation in the Kinai. After converging with Hideyoshi’s army, Nagamitsu served in the vanguard at the Battle of Yamazaki.
From the sixth month of 1586, he became seriously ill and, on 10/5, he died of illness.
Nagamitsu had a natural son, Aizō, and an adopted son, Tatsuchiyo, but after a struggle, Aizō succeeded him. Nevertheless, during the winter after his death, the Shiokawa family was crushed. His daughter wed Nobunaga’s eldest son, Oda Nobutada, and she may have been the mother of Oda Hidenobu.