Butterfly the chicken breast and pound it between two sheets of parchment paper until it is an even half-inch thickness.
Season both sides of the chicken with the sea salt and black pepper.
Prepare three shallow bowls: one with the flour, one with the beaten egg, and one with the panko breadcrumbs.
Dredge the chicken in the flour, shaking off any excess, then dip into the egg, and finally press firmly into the panko until fully coated.
Lightly brush or spray the coated chicken with avocado oil and place it in the air fryer basket.
Air fry at 400°F for 12 to 15 minutes, flipping halfway through, until the exterior is golden brown and the internal temperature reaches 165°F.
While the chicken cooks, thinly shred the green cabbage and toss it in a bowl with the sesame oil and rice vinegar.
Let the chicken rest for 2 minutes before slicing it into strips.
Serve the sliced katsu over the cabbage salad and drizzle with the tonkatsu sauce.