What is the name for the translucent thin sweet/sour flavored sheet that is sometimes placed on top of nigiri?

I have had this several times. It is a very thin sheet of something slightly crunchy and semi translucent (yellowish/brown tinge from what I remember) with a sweet and sour pickled flavor. I am assuming it is some kind of pickled daikon or seaweed.

Edit: https://thumbs.dreamstime.com/z/nigiri-sushi-various-types-turquois-plate-37539836.jpg?w=768

It’s the thin sheet on the second piece from the left.