Xuan Huaichang

Xu'an Huaichang (虛庵懷敞, Japanese: Kyōan Eshō, fl. late 12th century) was a Chinese Chan master of the Huanglong branch of the Linji school during the Southern Song dynasty, remembered above all as the teacher who transmitted the Zen patriarchal certification to the Japanese monk Eisai Myōan, thereby initiating the formal transmission of Rinzai Zen to Japan^[1]. Xu'an practiced and taught in the tradition that descended from Huanglong Huinan through several generations, incorporating elements of Daoist esoteric practice alongside Chan teaching in the syncretic style characteristic of late Song Buddhism. He was active at monasteries in Fujian and Zhejiang provinces^[1][2].

Eisai (1141–1215), during his second journey to China beginning in 1187, studied vinaya and Chan meditation under Xu'an Huaichang and received from him the formal certificate of Zen teacher — reportedly the first such certification granted to a Japanese student in China. Eisai returned to Japan in 1191 carrying both the lineage certification and seeds of the tea plant, launching the Rinzai school on Japanese soil and, as tradition has it, the Japanese tea ceremony. While subsequent Japanese Rinzai developed primarily through other Song lineages — especially through the Yangqi branch centered at Myōshinji — Xu'an's transmission to Eisai marks the institutional beginning of organized Zen in Japan^[2].