Xutang Zhiyu (1185 – 1269) was born in the Siming Xiangshan region in Zhejiang Province in China, also called "Zhiyu (Chigu)" and "Xigengsou (Sokkôsô)." After studying under Buddhist master Yuanan Puyan (Unnanfugan) and residing at a number of monasteries, he stayed at Guangli Temple (Kôri Temple) at Yuwangshan (Ikuô-zan) in 1258 (the 6th year of the Baoyou or Hoyûera) and Jingci Temple (Jôji Temple) at Nanshan (Nan-zan) in 1264 (the 5th year of Jingding era). He became the 40th Head Monk of Wanshou Temple (Manju Temple) at Jingshan (Kei-zan) in 1267 (the 3rd year of Xianchun era), but passed away two years later at the age of 85, a period in which he was entrusted and depended upon by Emperors Lizong (Risô) and Duzong (Takusô) of the Southern Song Dynasty.
Xutang Zhiyu wrote a letter addressed to another Zen Buddhist Wuweng Xiangyou. However, not much is known about what kind of person Wuweng was. Xutang Zhiyu was once pardoned for committing slander in the years 1253 – 1258 (the Baoyou or Hoyû era). The letter refers to that matter and shows that a visitor has traveled from afar to visit Dongshan (Tôsen) and expressed his gratitude for the hospitality that he has received. It is possible that the visitor mentioned in the letter was the Buddhist monk Nanbo Shômyô, who had come from Japan to study. It is presumed that Nanbo visited China in 1259 (the 1st year of the Kaiqing or Kaikei era) and returned to Japan in 1267 (the 3rd year of the Xianchun or Kanjun era) and the letter was written when Xutang was in his late seventies.