Tokushima Prefecture is a region where indigo dyeing is very popular. Its production accounts for the majority of the national market share. The indigo produced in Tokushima is called "Awa Ai". "Awa" is the old name of the Tokushima region. "Ai" means Indigo. The products of Awa Ai has been on the national market since the Edo period (1603-1868), and has brought great wealth to Tokushima's economy and culture. Indigo cultivation in Japan began in the Nara period (710-794). The plant, Aidate (Persicaria tinctoria), has been cultivated in the Yoshino River basin in Tokushima Prefecture. The area was not suitable for agriculture as typhoons often hit the area during the rice harvesting season in autumn. However, Aidate, which is cultivated before the typhoon season, is suitable for Tokushima's industry. Awa Ai, with its deep and bright blue color, is known overseas as "Japan Blue".