This is Japanese Bottarga, the dried and salted egg sacs of various species of mullet. Like its Mediteranean countepart it is a rich and powerful roe product and is used sparingly, either thinly sliced or ground up. Karasumi is one of the three famous gourmet delicacies of early Japanese Edo Period

Karasumi is a specialty of Nagasaki and along with salt-pickled sea urchin roe and Konowata one of the so-called three chinmi of Japan . It is made by desalinating salt pickled mullet roe and drying it by the sunlight. A theory suggests that it got its name from its resemblance to a block of sumi (India ink stick) imported from China (Kara) and used in shodo. Karasumi is a high priced delicacy and it is eaten while drinking sake.