The iyokan also known as anadomikan (穴門みかん), is a Japanese citrus

Citrus

Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...

 fruit. It is the second most widely produced citrus fruit in Japan after the unshū mikan

Mikan

The satsuma is a seedless and easy-peeling citrus mutant of Japanese origin introduced to the West.In Japan, it is known as mikan or formally unshu mikan . In China, it is known as Wenzhou migan . The Japanese name is a result of the local reading of the same characters used in the Chinese...

. It was discovered in the Meiji era in Yamaguchi Prefecture

Yamaguchi Prefecture

is a prefecture of Japan in the Chūgoku region on Honshū island. The capital is the city of Yamaguchi, in the center of the prefecture. The largest city, however, is Shimonoseki.- History :...

. It is now produced mostly in Ehime Prefecture

Ehime Prefecture

is a prefecture in northwestern Shikoku, Japan. The capital is Matsuyama.-History:Until the Meiji Restoration, Ehime prefecture was known as Iyo Province...

.

The peel is thicker than a mikan, but it can be peeled by hand. The flesh is slightly sour, but sweeter than a grapefruit.