There are many chain restaurants in Japan dedicated to this crispy cutlet.
In a small bowl, whisk the dry mustard and granulated garlic. Whisk in the Worcestershire, 1 tbsp. shoyu, and mirin. Whisk in the ketchup for the sauce
In a large strainer, sprinkle the cucumbers with the salt and sugar; toss until coated. Let drain for 20 minutes. Press on the cucumbers to remove any excess liquid. In a medium bowl, mix the cucumbers, apple, radishes, scallions, and shiso. Just before serving, mix in the vinegar, 1 tsp. shoyu, and sesame oil.
Meanwhile, using the bumpy side of a meat mallet, pound the pork to 1/8 to 1/4 inch thick. (If you have a flat meat mallet, pierce both sides of the cutlets with the tines of a fork after pounding them.) Season both sides of the cutlets with salt and pepper. In 1 shallow dish, place the flour. In a second, beat the eggs. In a third, place the panko. Line a rimmed baking sheet with paper towels or parchment paper; set a wire rack inside.
Pour enough peanut oil into a large skillet to measure about 1/4 inch. Working with 1 cutlet at a time, dredge the pork in the flour, shaking off any excess. Coat the pork in the eggs, letting any excess drip into the dish. Place the pork in the panko; turn until coated, pressing so the crumbs adhere. Working in batches, cook the pork, turning once, until crisp, golden, and just cooked through, about 5 minutes per batch. Add more peanut oil to the pan as needed between batches. Place the cutlets on the wire rack to drain.
Slice the cutlets. Top with the sauce. Serve with the salad.