Saeki Korenori served as the twelfth head of the Saeki clan and lord of Togamure Castle in the Amabe District of Bungo Province in Kyūshū.

Korenori’s father was Saeki Koretsune, the eleventh head of the clan, or his son, Koremasu.  The Saeki family lineage during this period is not certain.  In 1550, after an incident known as the Collapse on the Second Floor by which the head of the Ōtomo clan and family members were killed owing to an internal conflict over matters of succession, Korenori supported his lord, Ōtomo Yoshishige by gaining control of the capital city of Funai in Bungo, and thereafter became one of Yoshishige’s senior retainers.  That same year, Korenori fought in the vanguard against Kikuchi Yoshitake and his allies from Higo Province to suppress their rebellion.

The retainers of the Ōtomo were comprised of lineal family members as well as members from (illegitimate) branch families, with only family members having the privilege to display the family crest.  As the leading members of branch families, the Saeki clan opposed efforts by the Ōtomo to concentrate power.   Tensions between the families lingered from the time that Korenori’s grandfather, Saeki Koreharu, had killed himself after being accused by Ōtomo Yoshiaki, the twentieth head of the clan and Yoshishige’s father, of plotting a rebellion.

In 1556, Obara Akimoto, a member of a branch family, joined with other landholding families with local roots to launch a rebellion known as the Confrontation of Surnames.  The rebels opposed policies of Yoshishige and the lineal members of the clan.  Yoshiaki had stated in his final wishes that one-half of the senior retainers of the clan be chosen from among illegitimate members, but Yoshishige had favored the lineal family members, leading to the exclusion from this group of retainers from branch families such as Obara Akimoto.  The rebellion erupted in Funai, the home of the principal residence of the Ōtomo, causing Yoshishige to temporarily take refuge in Niujima Castle (later known as Usuki Castle) for protection.  Meanwhile, supporters of the lineal family members gained the upper hand, killing Honjō Munetsuna, Nakamura Naganao, and Kaku Koreshige in Bungo.  While Korenori did not directly participate in the rebellion, he maintained communications with Akimoto.  Nevertheless, Yoshishige directed forces against Korenori, whereupon Korenori gathered his family and fled for protection under Saionji Sanemitsu, lord of the Saionji clan in the southern portion of Iyo Province in Shikoku.  Korenori resided in that location for the next decade.

During the Eiroku era (1558-1570), conflict arose as the powerful Mōri clan from western Japan encroached on the territory of the Ōtomo in northern Kyūshū.  Naval forces formerly led by Korenori were critical as a means to counter the Mōri navy, causing Yoshishige to seek Korenori’s return to his domain.  In 1569, Korenori returned through the intermediation of retainers including Usuki Akisumi.  In 1570, Korenori was allowed to return to Togamure Castle and was further appointed as a member of the kahanshū, or senior retainers of the Ōtomo, following the departure of Bekki Akitsura to the Tachibana clan. In 1572, Yoshishige ordered the deployment of forces to Iyo in support of a battle by Ichijō Kanesada against the Saionji clan.  These forces attacked Yumori Castle and other locations, leading to the surrender of Saionji Kinhiro, a sengoku daimyō and eighth head of the clan.  In 1577, Korenori engaged in the rite of tonsure and adopted a monastic name.  His eldest son, Koremasa, inherited the clan.

Later that year, Itō Yoshisuke, the eleventh lineal head of the Itō clan of Hyūga Province lost in battle against the Shimazu clan and fled to the Ōtomo for protection.  The ensuing expansion of the Shimazu influence into northern Hyūga posed a threat to local families.  In the first month of 1578, news spread that Tsumochi Chikashige, lord of Matsuo Castle in northern Hyūga and a nephew of Korenori, had switched his allegiance to the Shimazu.  Korenori quickly intervened, urging Chikashige to reconsider, but to no avail, whereupon Yoshishige ordered Korenori to attack the Tsuchimochi.  Later that spring, Korenori led an assault against Matsuo, compelling Chikashige to surrender.  Korenori pled that Chikashige be spared, but Chikashige was forced to kill himself.

In the ninth month of 1578, Yoshishige sought to act on his beliefs by creating a seat of Christianity in Hyūga.  Ignoring protests from this retainers, he decided to personally deploy in preparation for an attack against the Shimazu.  At this time, Korenori remained in Matsuo Castle in Hyūga, whereupon Yoshishige ordered him to join the attack against Yamada Arinobu at Taka Castle.  Korenori encountered and defeated forces led by Shimazu Iehisa en route to protect Taka Castle, but the Ōtomo battalion under the command of Tawara Chikakata had low morale and the individual units did not collaborate well, so were unable to pursue the forces under Ieshisa, allowing them to enter Taka.  Meanwhile, upon learning that the primary contingent under Shimazu Yoshihisa was advancing to the north, the senior retainers of the Ōtomo held a consultation.  Korenori advised that the army maintain a siege and wait for the arrival of reinforcements under Shiga Chikamori, Kutami Akiyasu, and Ichimata Akizane from Higo Province.  Chikakata agreed while Takita Shigekane insisted the army should immediately press ahead or else die in the face of a surprise attack.  As predicted by Shigekane, the Shimazu forces launched an attack, and the Ōtomo forces were dragged into battle in the midst of chaos in an engagement known as the Battle of Mimikawa.  Korenori had no choice other than to advance with this troops, endeavoring to use his numerical superiority to pierce the center of the enemy contingent.  However, after forces led by Shimazu Iehisa came out of Taka Castle to attack, Chikakata ordered the entire army to retreat, triggering chaos among the fleeing forces.  The Shimazu exploited the situation by annihilating the Ōtomo forces.  Korenori, along with his sons, Koremasa and Shigetada were all killed in battle.  The clan was inherited by the son of Koremasa, Saeki Koresada.