Sushi always, most always begins with white fish sashimi known as she-row-me, and you’ll find either myoga a botanical ginger served as is, or some chefs lay raw fish over tsuma, a finely sliced daikon radish: https://mesubim.com/2014/04/01/tsuma-part-iv-slice-cut-video/

The white fish in spring is karei, with some punzu, or wasabi and salt, its a very delicate white fish that has its own identity. Some ask why no shoyu and the answer is, “having white pants and getting a spot spoils the white.”

The fish starts here and a logical sequence is followed, a progression from white to gai, bluefin, cephalopod and the final tastes are sea eel.