Hasegawa Masanobu was a wealthy landowner during the Sengoku period.  He served as the lord of Kogawa Castle in the Shida District of Suruga Province.

From the second half of the fifteenth century to the first half of the sixteenth century, Masanobu expanded his territory in Kogawa located in the Shida District of Suruga.  He was called the chief of Kogawa, or Hōei-chōja.

In 1427, Masanobu was born as the second son of Kanō Yoshihisa, the lord of the manor of Sakamoto and married into the Hasegawa family.

The Hasegawa clan is understood to have flourished by controlling distribution and trade at Kogawa Harbor located at the mouth of the Kuroishi River draining into Suruga Bay from the Shida Plains.  Accounts of the Imagawa family identify Masanobu as a member of a wealthy family in western Suruga.

In the second month of 1476, Imagawa Yoshitada, the eighth head of the Imagawa clan and military governor of Suruga, attacked kunishū, or provincial landowners, in Tōtōmi Province including Yokochi Shirōbei at Yokochi Castle and Katsumata Suri-no-suke at Katsumata Castle.  While returning to Suruga, at the Battle of Shiokaizaka, Yoshitada was attacked and killed by remnants of these clans.  At this time, his lineal heir, Tatsuōmaru (later known as Imagawa Ujichika) was still only six years old so retainers including the Miura and Asahina clans backed Oshika Norimitsu (the son of Oshika Noriyori, a cousin of Yoshitada), triggering a succession struggle.  The faction supporting Tatsuōmaru engaged in a flurry of battles against the faction backing Norimitsu.  Meanwhile, the Yokochi and Katsumata clans who were responsible for the death in battle of Yoshitada colluded with the Shiba clan and served Shiba Yoshisuke (later known as Shiba Yoshihiro) the military governor of Tōtōmi formally appointed by the bakufu.  By obstructing them, Yoshitada was viewed as a rebel toward the bakufu so rather than have his orphan, Tatsuōmaru, succeed to the headship of the clan, there was a possibility that he would be eliminated as a family member of a rebel.  Consequently, Tatsuōmaru’s mother, Kitagawa-dono, took him and fled for the protection of Masanobu, at Kogawa Castle.   Thereafter, Masanobu became a retainer of the Imagawa clan.

Kitagawa-dono then turned to her younger brother, Ise Moritoki (Sōzui), who at the time was serving as a member of the mōshitsugishū for Ashikaga Yoshihisa, the ninth shōgun of the Muromachi bakufu.  Upon orders of the bakufu, Moritoki mediated a solution whereby Norimitsu would serve in the role of a proxy as head of the clan at the Sunpu mansion until Tatsuōmaru became an adult.  Following this decision, Kitagawa-dono and Tatsuōmaru moved to the residence of the Saitō clan at Mariko Castle in Suruga.

In 1471, Masanobu founded the Rinsō Temple in his hometown of Sakamoto.  After his death in 1513, he was buried at this temple.

Anecdotes

Beginning in 1979, the ruins of Kogawa Castle were excavated and surveyed.  This resulted in the discovery of artifacts including ceramics imported from China that would have been owned by a wealthy family on the grounds of the former residence surrounded by moats and earthen mounds.  These findings substantiated the assessment of the Hasegawa as a wealthy clan.