Ryusan Tokuken (龍山徳見)

Ryusan Tokuken (1284 - December 22, 1358) was a priest of the Rinzai Sect from the late Kamakura period to the period of the Northern and Southern Courts. His secular surname was Chiba. Initially, his mina (personal name) was Riken, but later changed to Tokuken. His dogo (a pseudonym as a priest) was Ryuzan.
He was born in Shimosa Province
His shigo (a posthumous name) was Shingen Daisho Zenji (meaning a high-ranking Zen priest honored by the imperial court).

At the age of 13, he became a priest at Jufuku-ji Temple in Kamakura to study Buddhism under Jakuan Joso, and later practiced Zen meditation under Yishan Yining of Enkaku-ji Temple. At the age of 22, he went over to China (the Yuan Dynasty) and studied Zen meditation under Togan Jojitsu and Kurin Seimu in Mt. Tendo. He came back to Japan in 1349 after staying in Yuan for a long time, during which he studied the teachings of the Rinzai Sect, which ranges from those of Oryu (also known as Koryu) (a great Chinese priest) to those of Eisai (a Japanese Buddhist priest who studied in China, credited with bringing the Rinzai Sect of Zen Buddhism and green tea from China to Japan), and served as the chief priest of Tosotsu-ji Temple. He was appointed the position of juji (the chief priest) of Kennin-ji Temple in Kyoto by Tadayoshi ASHIKAGA, a younger brother of Takauji ASHIKAGA, and later served as the juji of Tenryu-ji and Nanzen-ji Temples as well.