Pat the chicken dry with paper towel. Keep the paper towels on the chicken and pound down until even thickness (if needed).
Preheat the air fryer at 400F for 5 minutes.
Set up your stations. In one plate, shallow container, or pie dish add the flour. In a second, add the whisked eggs. In a third, add the panko. Sprinkle salt on the top of each container.
Salt the chicken thighs to taste.
Cover the chicken in the flour, dip it in the egg, then cover it thoroughly in the panko mixture. Repeat with the other chicken thigh.
Spray the air fryer basket with oil. Place the chicken thighs. Liberally spray the chicken.
Air fry for 10-12 minutes, or until the chicken reaches safe internal temp (170F). Halfway through cooking, flip the chicken and spray with additional oil. If further crunchiness is desired, flip and spray with more oil during the last two minutes of cooking.
Katsu Sauce
Mix ingredients together in respective bowls. Store in an air tight container in the fridge until ready to use. Can make a day ahead.