However, when Muromachi bakufu was overthrown in 1573 and Yoshiaki came under the protection of the Mori clan, Kiyonobu left him and started to serve Nobunaga.
しかし、1573年（天正元年）年に室町幕府が滅び、義昭が毛利氏を頼ると清信は義昭と離れ、そのまま信長に仕えた。