Lifespan: Kyōroku 2 (1529) to fifth month of Tenshō 12 (1584)
Lord: Akamatsu Harumasa → Oda Nobunaga
Father: Kodera Norimoto
Siblings: Masamoto, Hiromine Nagamoto, Noriharu, sister (wife of Akamatsu Yoshisuke), sister (wife of Uozumi Yoshinaga), sister (wife of Kasuya Noriyori, Sadamasa)
Wife: Daughter of Kodera Tomimoto
Children: Ujimoto, Yoshiaki, Amakawa Masanori, Kasuga-hime, Koman-hime
Kodera Masamoto served as a bushō, head of the Kodera clan, and lord of Gochaku Castle in Harima Province.
Masamoto was born in 1529 as the eldest son of Kodera Norimoto, the lord of Gochaku Castle in Harima Province. The Kodera clan was a branch of the Akamatsu clan, and until the time of Masamoto’s grandfather, Kodera Masataka, was based at Himeji Castle in Harima.
From 1543, Masamoto resided in Shioda Castle to serve as a lieutenant of Kodera Tomimoto, a distant relative and lord of Shioda. In 1545, Masamoto succeeded his father as lord of Gochaku Castle. The Kodera clan served over multiple generations as senior retainers of the Akamatsu clan, the military governors of Harima. Masamoto received one of the characters in his name from Akamatsu Harumasa, the head of the Akamatsu clan. Thereafter, Masamoto kept in check several skirmishes while exercising quasi-independent authority over the plains of western Harima. Masamoto recognized the abilities of Kodera Yoshitaka (later known as Kuroda Yoshitaka), a tonosama, or outsider serving as a retainer of the Akamatsu. Masamoto maintained close relations with Yoshitaka, having his own niece (a daughter of the Kushihashi named Mitsu) wed him. In the late summer of 1558, Masamoto shunned Harumasa and promoted his eldest son, Yoshisuke, to become his new lord.
With the Oda approaching from the east and the Mōri from the west of Harima, Masamoto initially opposed Akamatsu Masahide of Tatsuno Castle and Bessho Yasuharu and Bessho Nagaharu (father and son) of Miki Castle who colluded with the Oda. In 1569, at the Battle of Aoyama and Kawarakeyama, he fought against the Akamatsu army. In 1573, he battled against the Bessho army at Masuiyama and Ariakeyama Castle. Thereafter, upon the urging of Kodera Yoshitaka, Masamoto decided to submit to Oda Nobunaga. In 1575, he dispatched Yoshitaka to Gifu, and within the same year, Masamoto himself paid visits under Nobunaga to the Akamatsu and Bessho clans. In 1577, the Mōri army launched a surprise attack on the coastline of Harima. Owing to Yoshitaka’s brilliant strategy, Masamoto helped defeat the attackers at the Battle of Aga. Around this time, Nobunaga ordered the heads of families in Harima to deliver hostages. In the case of Masamoto, his son, Ujimoto, was frail from illness, so he may have had the son of Kodera Yoshitaka, Shōjumaru (later known as Kuroda Nagamasa), turned over as a hostage instead. From this time forward, Kodera Yoshitaka began to serve as a commander of Hashiba Hideyoshi (who had been dispatched to Harima by Nobunaga) rather than as a retainer of the Akamatsu.
In 1578, Araki Murashige rebelled against Nobunaga at Arioka Castle in Settsu Province, triggering the Battle of Arioka Castle. Masamoto acted in coordination with this rebellion by betraying Nobunaga in favor of the Mōri clan. At this time, Bessho Nagaharu, lord of Miki Castle and the strongest power in eastern Harima, had already switched allegiance from the Oda to the Mōri. However, in 1579, the Oda army attacked and captured Arioka Castle, followed by Miki and Gochaku castles in 1580. Masamoto fled via Aga to Tomo-no-ura in Bingo Province under the control of the Mōri. He died in 1584 in Tomo-no-ura.
Masamoto’s wife, the daughter of his older brother (Kodera Tomimoto), died in the autumn of 1567. Moreover, his eldest son, Ujimoto, served the Kuroda clan, while his descendants served as members of the Fukuoka han for generations thereafter in the Edo period. The descendants of his second son, Yoshiaki, served for the Amagasaki han of the Aoyama clan, and later changed their surname to Akamatsu. After the fall of Gochaku Castle, another child named Amakawa Masanori was adopted by Okamura Hideharu and settled in Harima.