Kōgetsu Sogan (1574-1643) was the son of Tsuda Sogyo, a wealthy merchant in Sakai, Tennojiya. His alias was Kakushiko. He studied under Haruya Soen, a priest of Daitokuji Temple, from his childhood, and studied hard. In 1606, he received the title of “Etsuki” from Haruya. In 1610, he became the 156th abbot of Daitokuji Temple, and the following year, upon the death of Haruya, he took over Ryuko-in, the family temple of the Kuroda family. At the request of Nagamasa Kuroda, he also served as abbot of Sofukuji Temple in Chikuzen. Ezuki had many influential devotees, including Kobori Enshu and Sakuma Shokan. He learned the tea ceremony from his father, Tsuda Munenori, who served Oda Nobunaga and Toyotomi Hideyoshi as tea master, and was known as one of the leading cultural figures of his day. In the Shigoromo Incident, he protested to the Shogunate together with Sawan, Tamamuro, and others, and was questioned by the Shogunate, but was allowed to remain alone.