What do you think about these?
These are called wasabi, a kind of spice, and are mainly used for sushi and sashimi, sliced raw fish.
In sushi, a little wasabi is put between neta, sliced raw fish, and syari, rice with vinegar. People eat sashimi with soy sauce and a little wasabi.
The paste of wasabi is usually package in tube. But fresh wasabi, grated by metal or sharkskin grater, is much better and tasty than the paste.