The following year, in 1467 when the Onin War started, Toshihiro backed up Yoshikado SHIBA to make him new governor of Owari and took the side of the Western Camp led by Mochitoyo YAMANA.
翌年の応仁元年（1467年）の応仁の乱が起こると、新たな尾張守護として斯波義廉を擁立して、山名持豊率いる西軍側に付く。