Remove giblets and neck from both cavities. Rinse with cold water. Cut off wing tips and little tail as they may be caught in the fryer basket.
Combine soy sauce, sugar and 2/3 cup salt in a 40-60 quart pot. Submerge turkey in water. Add enough water to cover. Stir liquid to distribute the seasonings evenly. Cover and refrigerate 8 to 24 hours.
Remove turkey from brine, rinse well, removing all sugar and salt. Pat interior and exterior dry with paper towels. Drain brining liquid, rinse pot and dry it thoroughly (oil and water do not mix).
Stir together salt, black pepper and wasabi powder.
Rub spice mixture all over turkey, inside and out. Make sure neck hole is at least 2 inches in diameter, as oil needs to flow freely.
Set up turkey cooker outside, in an open area on a level dirt or grassy area.
Never fry a turkey indoors, in a garage or in any structure attached to a building. Do not fry on wood decks, which could catch fire, or concrete, which could be stained by the oil. (Safety tip: have a fire extinguisher nearby for added safety.)
Put 3+ gallons oil into pot and set it over medium-high heat. When oil reaches 375° F , place turkey into basket and lower it, very slowly, into oil. (Oil temperature will decrease at this point.) The level of the oil will rise due to the frothing caused by the moisture from the turkey but will stabilize in about one minute. (Safety tips: to prevent burns from the splattering oil , wear oven mitts/gloves, long sleeves, heavy shoes and even glasses. It is wise to have two people lowering and raising the turkey.)
Turn heat to high and return oil temperature to 365° F. Fry turkey for 3 to 4 minutes per lbs or about 35 to 42 minutes, or until it floats.
Stay with the cooker at all times as the heat must be regulated.
Carefully remove turkey from oil by lifting handle of basket. Let oil drain for a minute or so, back into the pot. Remove turkey and place on a cutting board. Use food thermometer to make sure thickest part of thigh registers 180° F ; if not, return to fryer and fry 10 more minutes, then repeat removal process.
Let turkey rest for about 15 minutes before carving.Servings: 12