In the Battle of Sekigahara in 1600, Takatsugu participated in the Western Camp at first and turned informer on movements of Western Camp such as Mitsunari ISHIDA and so on to the Eastern Camp.
慶長5年（1600年）の関ヶ原の戦いでは当初は西軍に与して石田三成ら西軍の動向を東軍に密告していた。