Koshu Oishi Tsumugi is a traditional silk fabric from the Oishi district, located on the north shore of Lake Kawaguchi in Yamanashi Prefecture, an area with a long weaving heritage. Records suggest that yellow-striped tsumugi was already being produced here during the Tenpo era. The term refers to textiles such as Oishi Tsumugi and Oishi Karaitoori (Chinese thread weaving), all made through an unbroken process that still integrates sericulture, silk reeling, twisting, dyeing, and weaving. Since ancient times, reeling machines have been used, and small quantities of tsumugi have featured silk floss threads for either the warp or weft. Today, under the official name “Koshu Oishi Tsumugi Weaving,” artisans produce fabric using the traditional method designated as a local craft in 1994—pre-dyed or plain white cloth woven from single-twisted silk threads for the warp and untwisted dupion threads for the weft.