Kogetsu Sogan was the son of Tsuda Sogyu (d. 1591), one of the San Sosho (Three greatest Tea Masters). He became a Zen monk of the Rinzai sect and the 156th head of Daitokuji Temple in Kyoto. He built the famous tea room Kohoan at Ryukoin, Daitokuji, commissioned by Kobori Enshu (1597-1647).
This calligraphy by Sogan is seven characters of a fourteen-character poem by the Tang-dynasty poet Liu Shang dedicated to Wang Yong:
Kimi sareba shunzan tareto tomonika asoban
Since you left Mount Shunzan, I have no friend to play with.