In a medium bowl, empty the can of tuna. Then add kewpie mayo, salt and the pickled radish. Mash with a fork until evenly mixed.
The fried fish cake usually comes frozen but defrosts quickly. You can heat these in an oiled pan to fry a bit or to defrost but this step isn’t absolutely necessary
Spread a thin layer of rice over the entirety of 1 sheet of nori. On one end, place a sheet of fish cake followed by a layer of tuna mixture, ending with one more sheet of fish cake.
Roll it up and slice. Top with eel sauce. Serve and enjoy!