It is a plant that resembles sesame leaves when only looking at the leaves, and it is called Shiso or Perilla. In Japanese, it is referred to as Shiso (紫蘇), with the Chinese characters pronounced directly in Japanese. There are two types of Shiso: Green Shiso and Purple Shiso, with the latter derived from the purple variety. The blue-colored Shiso is called Aojiso (青じそ), but it is commonly known as Oba (大葉).
According to one theory, a young person in China ate a crab and died, but he was revived by consuming a preparation made from purple Shiso leaves. The name "Shiso" originated from the meaning of a leaf turning purple and bringing about revival. In sushi, Shiso and ginger are finely chopped to make "薬味yakumi" and are often placed on top of blue-skinned fish or thinly sliced and placed on top of sushi rice in the case of white fish or squid sushi.