[1] As a child, Nobuyasu was sent to the Imagawa capital of Sunpu, located in Suruga Province (modern-day Shizuoka Prefecture) as a hostage.

Later, he was named keeper of Okazaki Castle in Mikawa Province (modern-day Aichi Prefecture), the birthplace of his father, and took part in the Battle of Nagashino in 1575.

When Nobunaga brought the allegations to the attention of Ieyasu, he had his wife confined and then executed, to allay any suspicions of his ally.

The possibility of revenge was an unacceptable risk to Ieyasu, and the only solution was that Nobuyasu should kill himself for the integrity and security of the clan.

In particular, supposedly Sakai Tadatsugu declined to refute any suspicions of treason, due to his personal disregard for Nobuyasu.