Aso Koremitsu served as a daimyō during the Azuchi-Momoyama period in Higo Province. He further served as the high priest of the Aso Shrine in Higo.
In 1582, Koremitsu was born as the eldest son of Aso Koretane.
In 1584, owing to the death of his father, Koretane, Koremitsu became the head of the clan at the age of two.
On 7/3 of Tenshō 13 (1585), Kai Sōun died, leading to an offensive by the Shimazu clan of Satsuma Province. On 8/12, Hanayama Castle was felled. At the end of the eighth month, the Shimazu forces captured Kashida and Kiyama castles. Seeking to surrender, the Aso family dispatched a monk from the Sōgen Temple in Yatsushiro. The Shimazu, however, rejected a settlement. In the ninth month, retainers of Kai Sōun were executed one after another. Koremitsu and his younger brother, Aso Koreyoshi, were taken by their mother who fled to Mount Memaru. After Toyotomi Hideyoshi commenced the campaign known as the Pacification of Kyūshū, she sought their protection, whereupon Sassa Narimasa took custody of Koremitsu.
On 6/25 of Tenshō 15 (1587), Toyotomi Hideyoshi granted the modest amount of 300 chō in Yabe in Higo to Koremitsu. In the seventh month, upon the outbreak of the Higo Kokujin Uprising, Hideyoshi ordered the execution of Koremitsu. At this time, however, Koremitsu was located in Kumamoto Castle so it became clear that he was not implicated in the uprising and was absolved of the charge. Instead, Sassa Narimasa was executed upon suspicion of instigating the rebellion, while Katō Kiyomasa was given custody of Koremitsu who was only six years old at the time.
In the sixth month of 1593, following the outbreak of the Umekita Uprising, Koremitsu was suspected of colluding with Shimazu Toshihisa and Umekita Kunikane, whereupon he was ordered by Hideyoshi to commit seppuku. On 8/18 of Bunroku 1 (1593), Koremitsu obeyed the verdict by committing seppuku on Mount Hanaoka at the age of twelve. This was intended to occur while Kiyomasa was away on deployment for the Bunroku Campaign on the Korean Peninsula.
Later, Koremitsu’s younger brother, Aso Koreyoshi, was called upon by Kiyomasa to serve as the high priest of the Aso Shrine, restoring the role of the family as the stewards of the shrine.