The iyokan (伊予柑), also known as anadomikan (穴門みかん) and Gokaku no Iyokan, is a Japanese citrus fruit. It is the second most widely produced citrus fruit in Japan after the unshū mikan. It was discovered in the Meiji era in Yamaguchi Prefecture. It is now produced mostly in Ehime Prefecture. The peel is thicker than a mikan, but it can be peeled by hand. The skin is very shiny and brightly colored and once peeled, the flesh has a very strong scent wafting out. The flesh is slightly sour and more bitter than an orange, but sweeter than a grapefruit. There is a variation grown into a pentagon shape to promote good luck and to revive the popularity of the fruit, also giving it another nickname, Gokaku no Iyokan, which translates into 'sweet smell of success in exams.' It is sometimes placed into fish feed to improve the fish's flavor.