Sashimi konnyaku 刺身こんにゃく
This food is sashimi konnyaku さしみこんにゃく.
Konnyaku is a traditional food and made from the root of a plant of Araceae family such as taro.
It has unique in texture like a hard type of jelly.
Sashimi konnyaku is a kind of konnyaku, but it is made softer than normal konnyaku and usually seasoned with nori.

Sashimi konnyaku 刺身こんにゃく
Sashimi konnyaku 刺身こんにゃく、さしみこんにゃく About 100 yen (US$1)
Sashimi konnyaku 刺身こんにゃく
First, wash sashimi konnyaku with iced water.
Sashimi konnyaku 刺身こんにゃく
Next, drain off the water from it.
Then, put the sauce on it.

At a supermarket in Japan, I recommend finding sashimi konnyaku. It includes a pack of sauce called Karashi-su-miso からし酢みそ. This sauce and sashimi konnyaku matches very well. It is made from miso, mustard, vinegar and sugar. You could also put a little bit of wasabi and soy sauce on it instead of Karashi-su-miso.

Note
You can probably buy Sashimi konnyaku in supermarkets in Japan, but please make sure you should find the name 刺身こんにゃく or さしみこんにゃく, because normal konnyaku こんにゃく usually requires boiling while
Sahimi konnyaku doesn’t require boiling.
Eating normal konnyaku without boiling and seasonings is not tasty.
However, konnyaku is already boiled in the manufacturing process.

Sashimi means sliced raw seafood or meat.
But sashimi konnyaku is not made from those foods and isn’t raw, but it is like sashimi in texture.
It is good for vegetarians.