Yasutane was the son of Shiina Yoshitane. He ruled his domain in Etchû province from Matsukura castle. He clashed with neighboring Jinbo Nagamoto, lord of Toyama castle, throughout the 1550's, briefly making peace in 1554 through the mediation of the Hatakeyama of Noto province. In 1560 Yasutane was able to secure the support of the Uesugi clan, and in April Uesugi Kenshin brought down Toyama. The Jinbo and Shiina continued to fight, and later Yasutane entered into an agreement with the Takeda of Kai. This provoked Kenshin, who in 1575 attacked and captured Matsukura. Yastutane petitioned Kenshin to return Matsukura to him but this did not occur. The Shiina thus became vassals of the Uesugi but did not survive the 1578-79 Ôtate no ran.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005