After the death of Shingen TAKEDA, in August 1573, Sadamasa OKUDAIRA (later known as Nobumasa OKUDAIRA), who was a vassal of the Takeda family, switched to the TOKUGAWA side with his all family members and retainers, following his father Sadayoshi OKUDAIRA who made the bold decision.
1573年8月、武田家家臣であった奥平貞昌（後の奥平信昌）は武田信玄の死に際し、父・奥平貞能の英断により一族郎党を連れて徳川方へ寝返る。