Nagayoshi was the second son of Mori Yoshinari and the son-in-law of Ikeda Nobuteru. He was given Kaneyama Castle in Mino on the event of his father's death in battle. While in the service of Oda Nobunaga he was often under the command of Oda Nobutada, Nobunaga's eldest son. He fought at Nagashima in 1574 and was with Nobutada at the 1582 reduction of the Takeda's Takatô Castle in Shinano province. Immediately afterwards he pressed onward without permission and took a number of castles in Shinano before entering Kazu Castle in Kai, which he set about fortifying. For his efforts he was awarded a fief in Shinano worth some 100,000 koku. He was however forced to withdraw from the province after the death of Nobunaga and took up in Mino with his relatives, the Ikeda. He was under the command of Ikeda Nobuteru in the 1584 Komaki Campaign and joined him on a flanking move designed to force Tokugawa Ieyasu’s retreat from Owari province. Confronted by Tokugawa forces at Nagakute, he rode at the head of his men and was shot and killed.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005