- Born: 1658
- Died: 1714/11/2
- Titles: soba yônin (1688-?), Rôjû & Tairô (1706/1/11-1709/6/3), Dewa-no-kami, Mino-no-kami
- Other Names: 柳沢保明 (Yanagisawa Yasuakira), 松平吉保 (Matsudaira Yoshiyasu), Fusayasu, Yatarô, Hozan, Shôshô Yoshiyasu
- Japanese: 柳沢吉保 (Yanagisawa Yoshiyasu)
Previously known as Fusayasu and Yasuakira, he was born into a samurai family, and was initially a mere page (koshô) to the fourth son of Shogun Tokugawa Iemitsu, Tokugawa Tsunayoshi, with a stipend of 150 koku. He became one of Tsunayoshi's favorites, and after Tsunayoshi became shogun in 1680, he was granted use of the character yoshi from Tsunayoshi's name, taking on the name Yoshiyasu.
In 1688, Tsunayoshi granted Yoshiyasu daimyô status (with a fief of 32,030 koku) and the position of soba yônin. He was later visited directly at his home by the Shogun on nearly sixty occasions, beginning with a visit on 1691/3/22. In 1701, Tsunayoshi granted Yoshiyasu the privilege of the use of the surname Matsudaira.
Yoshiyasu became lord of the 150,000 koku domain of Kôfu in 1704, and then rôjû and Tairô in 1706, serving in that position until 1709. At the peak of his status, he claimed a fief of some 228,765 koku. Due to the responsibilities associated with his high-ranking position in the shogunate, however, it is unclear if Yoshiyasu ever in fact traveled to Kôfu.
He is known as an avid patron of Chinese thought and culture, inviting a number of Chinese Ôbaku Zen monks, as well as Nagasaki-based Japanese scholars of colloquial Chinese language and culture, to his mansions, and appointing Ogyû Sorai as a scholar in his service. Yanagisawa also sponsored discussions, sometimes attended by the shogun, of Confucian classics, conducted in Chinese; in connection with this, he also organized language classes in colloquial Chinese which served as the basis for Sorai's own study of the language. When the Chinese monk Yuefeng Daozhang was interviewed by Tsunayoshi in 1705, it is said that Yanagisawa was the only one in the room who did not need to wait for the interpreters to understand what was being said.
His engagement with Chinese language and Zen Buddhism is said to have begun around 1677, when at 20 years old he began frequenting the Ryûkô-ji and other Rinzai Zen temples in Edo. In 1692, he met Gaoquan Xingdun, the fifth abbot of Manpuku-ji; after this initial meeting, Yoshiyasu regularly received Gaoquan whenever the monk came to Edo, and in 1695 Yoshiyasu officially became his disciple. Though Gaoquan died later that same year, Yoshiyasu maintained contacts with subsequent heads of the Manpuku-ji, including especially Yuefeng Daozhang. Yuefeng established the Eikei-ji in Kai province in 1708 as a personal family temple (bodaiji) for Yoshiyasu, and the following year, after the death of Shogun Tokugawa Tsunayoshi, Yuefeng conducted the ceremonies in which Yoshiyasu and his wife Soshi Sadako (1661-1713) took the tonsure.
- Arai Hakuseki, Joyce Ackroyd (trans.), Told Round a Brushwood Fire, University of Tokyo Press (1979), 311n31.
- Plaques on-site at Rikugien.
- Rebeckah Clements, "Speaking in Tongues? Daimyo, Zen Monks, and Spoken Chinese in Japan, 1661–1711," The Journal of Asian Studies Vol. 76, No. 3 (August) 2017: 604-605.
- Cecilia Segawa Seigle, “Tokugawa Tsunayoshi and the Formation of Edo Castle Rituals of Giving,” in Martha Chaiklin (ed.), Mediated by Gifts: Politics and Society in Japan 1350-1850, Brill (2017), 131-133.
- Clements, 605.
- Marius Jansen, China in the Tokugawa World, Harvard University Press (1992), 56-57.
- Clements, 610.
- Clements, 610.