Put 100 g of tempura batter mix in a glass bowl and mix it with 160 ml of cold water.
Sprinkle 50 g of Japanese Panko bread crumbs (or more, depending on the number of crabs) on a plate.
Dip the soft-shell crab in the tempura batter, then roll it in the bread crumbs.
Deep fry until golden brown. This should take two to three minutes or less.
Let the fried crab cool on a paper towel. The paper absorbs excess fat.
Enjoy the soft-shell crab either on its own or inside a soft-shell crab sushi roll.