A uniquely Japanese unit that appears in the Kojiki (Records of Ancient Matters) and Nihon Shoki (Chronicles of Japan). It is the width of 4 fingers. It was used to express the length of an arrow even after units such as shaku had come from China. An arrow fired by Nasu no Yoichi in the Genpei Yashima battle was 12 tsuka and 2 buse. The “buse (fuse)” refers to the width of one finger, so it is equivalent in size to the “digit” (see p. 90).