This KitKat is sold exclusively in the Chugoku and Shikoku regions and supposedly uses citrus fruits from the same regions. The flavor is a balance of Onshu Mikan, Lemon and Sudachi citrus fruits (温州みかん, レモン, すだち). Sudachi is a special Japanese citrus variety and Onshu Mikan is a variety of mikan named after a city in China. This variety might have originally been mistaken as having been derived from China, but DNA evidence shows that it actually originates from Kagoshima Prefecture, Japan instead. The name 柑橘黄金 translates as Golden Citrus. ネスレ、キットカット
Photo is a web capture for explanatory purposes, copyright belongs to the company.