In a mixing bowl, combine all ingredients for the seasoned flour.
In a separate mixing bowl, combine dry ingredients for the tempura batter. Beat the egg and cold water together in a separate container. Add egg and water mixture to the dry ingredients and mix.
In another mixing bowl, combine the furikake and panko flakes. Line up the 3 bowls in the following order: Seasoned flour, tempura batter, furikake coating. Season the fillets in the seasoned flour. Dip it into the tempura batter and then coat it with the furikake-panko mixture.
Heat a deep pot halfway filled with peanut oil to 350 degrees F. Fry the ahi in the oil until brown, turn and fry for an additional minute. Drain and serve while hot.