Mix sesame seeds in a shallow dish. Sprinkle tuna steaks with salt & pepper on both sides. Dredge in seeds until coated on all sides.
Warm oil in a pan over med-high heat until smoking. Place tuna in pan and cook until white sesame seeds begin to turn golden about one minute. Turn tuna and cook until the white sesame turns golden on the other side.
Remove from heat and cut into 1" thick strips. Serve with pickled ginger, wasabi, and soy sauce.