Hi, I love sushi. there is a great place where I live that makes great sushi
I'm vegetarian, which rules out the raw seafood! But I have had sushi with vegetables, which was quite good. I love the wasabi that comes with it!
That stuff is sometimes too hot for me. I like the flavor of the rice. There are a lot of different styles and presentations vary a lot too,
I like that it can be prepared with white rice or brown rice, depending on its type. The other thing I love is the pickled ginger.
I like the Daikon radishes too. It is sometimes confused with sashimi which is just thin sliced raw fish with optional serving of rice.
Yes, daikon radish is a very popular garnish. My favorite rice is brown rice as its better for you and tastes nuttier.
The rices usually have a vinegar and spices mix that give it flavor. It's then cooled and shaped. 
I believe it also preserves it. How smart the Japanese are! They began adding it to the sushi prep. in the 14th century.
The black seaweed wrappers are actually a type of algae.