In a small bowl whisk together the soy sauce, vegetable oil, mirin and garlic. Season the ribs all over with salt and pepper and rub with the marinade. Add the ribs to a platter, cover and refrigerate for at least 1 hour and up to overnight.
Remove the ribs from the refrigerator and let them come to room temperature for 30 minutes before cooking.
Heat oven to 325ºF (170ºC). Add racks of ribs to a large baking sheet (or 2 if needed). Cover the baking sheets with aluminum foil and bake until the ribs are tender but not falling off the bone, about 2 hours.
Remove the ribs and set aside to cool. Heat the oven to broil on high. Cut into individual ribs and return the ribs to the baking sheet, turning to coat in any remaining sauce on the baking sheet. Broil, turning occasionally, until charred in spots, about 5 minutes.
Remove the ribs from the oven and let sit for 5 minutes. Arrange the ribs on a platter and dust with the Shichimi togarashi.
For the herb salad:
Combine the cilantro, green onion, cucumber and shallots in a small bowl. Toss with the remaining cooking juices.