Background
Masanobu Kosaka was born in 1526 in Kai Province (Yama-nashi Prefecture).
Masanobu Kosaka was born in 1526 in Kai Province (Yama-nashi Prefecture).
Masanobu Kosaka was made castellan of Komoro Castle (Nagano Prefecture) in 1553. Fortified Kaizu Castle for defense against Hokunku District in 1556. As the general in command of Kaizu castle, Kosaka played an important role in the fourth Battle of Kawanakajima. He informed Takeda via signal fires of the movements of Uesugi Kenshin's army as it approached, and then led the sneak attack up Saijo-yama in order to drive Uesugi's men down to the plain where they could be surprised by Takeda's army. Even though that tactic failed, Kōsaka led his men back down the hill, attacking Uesugi's army from the rear, turning the tide of the battle.
After the death of Shingen Takeda his troops became demoralized and were miserably defeated by the armies of Oda and Tokugawa. Out of humiliation for this he died in sorrow. He died on June 12, 1578.
Masanobu Kosaka was calm and cool by nature and never took unnecessary risks, for which he was nicknamed "Flying Danjo."
The association between Masanobu and Shingen began in 1543 as a love relationship. At the time they were 16 and 22, respectively. Such relationships were in vogue in pre-modern Japan, a tradition known as shudo. The love pact signed by the two, in University of Tokyo's Historical Archive, documents Shingen's pledge that he was not in, nor had any intentions of entering into, a sexual relationship with a certain other retainer, and asserts that "since I want to be intimate with you" he will in no way harm the boy, and calls upon the gods to be his guarantors.
