Upon the establishment of a bond between the Oda clan and the Azai clan through marriage, Nagakatsu accompanied Oichi no Kata (Lady Oichi), the sister of Nobunaga ODA, to the Azai clan for which he came to serve.
織田氏と浅井氏との婚儀に際しては、永勝は信長の妹お市の方に随伴して浅井氏に仕える。