Lifespan: Eishō 10 (1513) to 9/11 of Kōji 3 (1557) or Eiroku 5 (1562)
Other Names: Tōtarō (common)
Title: Governor of Nagato (honorary)
Lord: Imagawa Yoshimoto
Father: Udono 長将
Siblings: Nagamochi, 長成, Nagasuke
Wife: Daughter of Imagawa Ujichika (younger sister of Imagawa Yoshimoto)
Children: Nagateru, Nagatada, Nishi-no-kōri-no-tsubone, daughter (wife of Matsudaira Koretada), Otazu-no-kata
Udono Nagamochi served as a bushō during the Sengoku period. He was a retainer of the Imagawa clan.
Nagamochi was the lord of Kaminogō Castle in the Hoi District of Mikawa Province. He was married to the younger sister of Imagawa Yoshimoto. In 1557, he died and the headship of the clan was inherited by his lineal heir, Udono Nagateru. According to historical accounts of Mikawa, he died in 1562. In the fifth month of 1560, at the Battle of Okehazama, he assisted in the liberation of Ōdaka Castle in Owari which had been under siege by the forces of Oda Nobunaga. Imagawa Yoshimoto, however, was killed in an attack by the Oda army on the main division of the Imagawa trailing behind, after which Nagamochi fled back to his territory in Mikawa. Thereafter, owing to his position as a relative of Yoshimoto, he remained loyal to the Imagawa, faithfully carrying out his duties as a retainer of the clan in Mikawa. A cadet family of the Udono located nearby joined Ieyasu based in Okazaki so that Nagamochi was left isolated on the front lines of the Imagawa. In 1562, he incurred an attack by forces aligned with Ieyasu. Although he halted the assault by advance forces including Matsudaira Kiyomune, once Ieyasu’s main division from Okazaki joined, Nagamochi could not hold back the opposing forces and Kaminogō Castle fell. Nagamochi, along with his son, Nagateru, was killed in action.
His grandsons, Udono Ujinaga and Udono Ujitsugu, were apprehended and tendered as hostages to the Matsudaira clan. In exchange for their return, Ieyasu demanded the release of his formal wife (Sena or Tsukiyama-dono), his lineal heir (Takechiyo), and his eldest daughter (Kamehime) who were tendered as hostages to the Yoshimoto during the period that he was under the command of the Imagawa clan. Nagamochi’s formal wife was the younger sister of Yoshimoto so Ujinaga and the Udono family who loyally served the Imagawa family were close relatives of Imagawa Ujizane (the lord of the Imagawa clan at the time).