Pat the duck breasts completely dry with paper towels. Using a very sharp knife, score the skin in a crosshatch pattern, cutting about 1/8 inch deep through the fat layer but being careful not to cut into the flesh beneath. This allows the fat to render properly and the skin to crisp up beautifully.
Season both sides of the duck breasts with the kosher salt, black pepper, garlic powder, and five-spice powder. Rub the seasoning into the scored skin. Let them sit at room temperature for 15 to 20 minutes while the air fryer preheats.
Preheat the air fryer to 360 degrees F for 3 minutes.
Place the duck breasts skin-side up in the air fryer basket. Air fry at 360 degrees F for 12 minutes. The lower temperature allows the fat under the skin to slowly render without burning.
After 12 minutes, increase the temperature to 400 degrees F and continue cooking for 3 to 4 more minutes to crisp the skin. The internal temperature should read 130 to 135 degrees F for medium-rare, which is ideal for duck breast.
While the duck finishes cooking, whisk together the honey, soy sauce, and rice vinegar in a small bowl to make a simple glaze.
Transfer the duck breasts to a cutting board and rest for 5 minutes - this is essential. After resting, slice each breast against the grain into thin slices on the bias. Fan the slices out on a plate and drizzle the honey-soy glaze over the top. Serve immediately.