The Zen priest Jakushitsu Genko (also known as Zen Master En'no, 1290-1367) was the successor of the Zen priest Yakuo Tokken (1244-1319) and went to China in 1320. After returning to Japan in 1360, he received the patronage of the warlord Sasaki Ujiyori (1326-70) of Omi Province and became the founder of the Rinzai Zen temple Eigen-ji. This letter is thought to have been written to his dharma brother (senior disciple) of Tenryu-ji Temple in Kyoto, Kezo'in. From its content, which informs the reader of a confrontation with the army of the warlord Shiba Takatsune, the letter appears to date to the year Joji 5 (1366). It also mentions Ujiyori's continued protection.