Life and Career
Masatoshi was the third son of Hotta Masamori, Tairô under the previous shogun, Tokugawa Iemitsu, who committed seppuku upon Iemitsu's death in 1651. Masatoshi was then adopted by Iemitsu's nurse, Kasuga no Tsubone, at the order of the late Iemitsu.
He served as lord of Annaka han in Kôzuke province, and personal secretary to the next shogun, Tokugawa Ietsuna, for a time, before being appointed wakadoshiyori (junior councillor) in 1670. He then served as lord of Koga han in Shimousa province for a brief period; Shogun Tokugawa Ietsuna was already quite ill when Masatoshi was appointed rôjû in 1679, and died the following summer. At this time, another rôjû, Sakai Tadakiyo, in a bid for personal power, proposed that the next shogun be selected from the princely houses. He sought to be regent to this new shogun, who would be made a puppet ruler. However, Masatoshi, said to have been infuriated, voiced strong opposition to this scheme; Tadakiyo resigned his post shortly afterwards, and Ietsuna's brother Tokugawa Tsunayoshi was installed as the new shogun.
Masatoshi became Tairô soon afterwards, and was granted a domain worth 13,000 koku by Tsunayoshi. He was killed several years later, in 1684. The motives of the culprit, Masatoshi's cousin Inaba Masayasu, are unknown. Following Masatoshi's death, Tsunayoshi took the opportunity to reorganize the shogunate's offices so as to weaken the rôjû and grant additional powers to the Soba-yônin (Chamberlains). Masatoshi was not succeeded as Tairô, and much of his power came to be wielded by the shogun himself.