Mentaiko in Japanese and called Myeongranjeot in Korean refers to the marinated cod or pollock roe (eggs) which is used as a common ingredient in both Japanese and Korean Cuisines and is usually made from variety of flavors and colors.
It is usually eaten by itself or with Sake and Onigiri. Nowadays it becomes popular in other Asian countries like Thailand as a sauce for spaghetti mixed with butter or mayonnaise.
Karashi Mentaiko is a variety of Mentaiko which is spicy and is a product of Fukuoka City in Japan