Akechi Hidemitsu served as a senior retainer of Akechi Mitsuhide and the Oda clan.  Hidemitsu was the son-in-law of Mitsuhide.    According to historical accounts, Hidemitsu variously originated from the Miyake, the Akechi, or the Tōyama clans.  Based on the accounts that link him to the Akechi, Hidemitsu grew up under the care of Akechi Mitsuyasu, lord of Akechi Castle in Mino Province.

In 1578, his daughter wed Akechi Muratsugu, the eldest son of Akechi Murashige, but the couple separated after Murashige rebelled against Oda Nobunaga. Mitsuhide assigned Hidemitsu to serve as lord of Fukuchiyama Castle in Tanba Province after its construction in 1579.  On 6/2 of 1582, Hidemitsu served as one of the leaders in the coup d’état against Nobunaga at the Honnō Temple Incident in Kyōto.  He then briefly defended Azuchi Castle and provided rear-guard support for Akechi Mitsuhide in the Battle of Yamazaki against Toyotomi Hideyoshi.  Facing defeat at the hands of Hori Hidemasa, a retainer of Hideyoshi, Hidemitsu fled to Sakamoto Castle in Ōmi.  

With the castle surrounded by men under Hidemasa’s command, Hidemitsu could not stand the thought of Mitsuhide’s valuable treasures and possessions being taken along with the castle, so he created a manifest of the items and lowered them down from the turret to where the enemy forces were located, shouting for them to care for the valuables.  When questioned in regard to the whereabouts of a wakizashi, or short sword, from a major battle led by Minamoto no Yoshinaka at Kurikara Ridge in 1183, Hidemitsu noted that he wished to wear it and return to Mitsuhide in the afterlife.  Thereafter, Hidemitsu slayed Mitsuhide’s wife, children, and his own wife, set the castle on fire and committed suicide, while his father was later executed that same year.