Koseto is the generic name for tea caddies made by Fujishiro Keisho I, who used Japanese clay and glaze after returning from the Sung Dynasty in China. The large ones are called “Oseto” and the small ones “Kosedo”. Koseto is also known as Nenuki Koseto. In “Chawaniki Bengokushu,” it is written, “I. The clay is shallow yellow, and the dark and light colors change according to the tea caddy, and also the clay is splendid, with rat-colored clay and light red clay. There is also a tea caddy with a black face on top of the ground medicine, a light black color with a middle black sesame medicine on top of the top medicine, a dark persimmon medicine with a light black color on top of the bottom medicine, a light red color with a little blackish candy medicine on top of the bottom medicine, a medicine with a blue color on the edge of the mouth, but it looks a little pale, it is also called a nashimayaku or tea medicine and is a medicine that is promised to be taken by the root extraction. The body of the tea caddy has a swelling like a grain of soybeans. The tea caddy is a rare example of a tea caddy with a four-sided shoulder, a round pot, an eggplant, a gourd, an uchikai, a tebin, and an ear, and large tea caddies are rare. The “Novel of Honcho Ceramics” also mentions a technique called “kosedo sembite” (kosedo sembite). (Chawaniki Bengyoshu, Honcho Pottery Novelogue, Chado Sentei, Hoshu-an Kiln Branch, Kokin Meimono Ruiju, Koryo Chawan and Seto Chajiryu, etc.)
