Lifespan: Eiroku 1 (1558) to 9/14 of Kanei 10 (1633)
Other Names: Kumachiyo (childhood), Gobei, Chōzaburō, Iki-no-kami, Shichiemon (common)
Title: Governor of Mimasaka
Domain: Mutsu-Tanagura, Chikugo-Yanagawa
Lord: Tachibana Dōsetsu → Tachibana Muneshige
Father: Yufu Korenobu
Mother: Daughter of Yufu Korekatsu
Siblings: Koresada, Koretsugu, Korenori, sister (wife of Tajiri 宗仙)
Wife: Daughter of Yufu 碁晨
Children: Daughter (wife of Tachibana 惟与), Korenaga
Adopted Children: Tachibana 惟与 (son-in-law)
Yufu Koretsugu served as a bushō during the Azuchi-Momoyama and early Edo periods. He was a retainer of the Tachibana clan.
In 1558, Koretsugu was born as the son of Yufu Korenobu. In 1570, Koretsugu, together with his father and younger brother, obeyed Tachibana Dōsetsu and headed toward Chikuzen Province. As a hereditary retainer of Dōsetsu, he joined his father in battles across Chikuzen.
Supporters of the Tachibana transported provisions to Takatoriyama Castle in Chikuzen held by Mōri Shigezane, a retainer of the Ōtomo clan. On 11/13 of Tenshō 9 (1575), on the route back, Koretsugu fought against the Sugi and Akizuki clans, in addition to retainers of the Munakata clan, at the Battle of Koganehara. Through skillful use of the arquebus, he shot the enemy commander, Kawazu Shuri-no-jō, and captured his head. In the course of this battle, he incurred injuries from swords and spears in thirteen locations on his body and later received a written commendation for his sacrifices. Thereafter, his legs were disabled so he served as a magistrate and remained on base. In 1597, during the Keichō Campaign on the Korean Peninsula, he led 367 soldiers in the third division of the Tachibana army and participated in naval battles. His younger brother, Yufu Korenori, was killed in action during his deployment in Korea.
In 1596, Koretsugu inherited from his father, Korenobu, the headship of the clan and a stipend of 3,500 koku. In 1599, his son-in-law, Tachibana 惟与 inherited the headship of the Yufu clan. After the Battle of Sekigahara, the Tachibana family was removed from its position while Koretsugu and his family followed Muneshige and became rōnin, or wandering samurai. In 1603, Muneshige was spotted by Tokugawa Ieyasu, the first shōgun of the Edo bakufu, and appointed as the first lord of the Mutsu-Tanagura domain with a fief of 10,000 koku. While Muneshige was in Edo to attend to the shōgun, Koretsugu and Korenobu managed the administrative affairs of the domain.
Later, in 1620, after the reassignment of the Tachibana family to Yanagawa, Koretsugu served as an elder and, together with 惟与, managed administrative and diplomatic affairs. His son-in-law, 惟与 (the eldest son of Totoki Tsuresada) succeeded to the headship of the clan and adopted the Tachibana surname.