During the Battle of Sekigahara in 1600, Kanetoshi sided with the 'western' army, and at a preliminary skirmish on August 16th, Kanetoshi fought a loosing battle against the enemy troops of the 'eastern' army led by Nagakatsu ICHIHASHI and Nagamasa TOKUNAGA, resulting in abandoning his Fukutsuka-jo Castle and taking refuge at Ogaki-jo Castle.
慶長5年（1600年）、関ヶ原の戦いにおいて西軍に属し、8月16日の前哨戦で、東軍の市橋長勝、徳永寿昌と戦い、敗れて居城の福束城を放棄して大垣城に逃亡する。