The Japanese leek is a little different from regular leek. It is thinner and does not have a hard layer inside. Instead, there is a soft centre that melts when cooked. Taste wise, the Japanese leek is very sweet. There are many varieties of Japanese leeks available in Japan and most of them become sweet when cooked. To store, wrap leek in newspaper or put in a plastic bag and keep in the refrigerator standing up. This will keep the leek fresh for a longer time. You can also chop the leek up and store in the freezer.