In a small bowl, combine the soy sauce, oil, togarashi, and garlic. Pour three-quarters of the marinade into a baking dish and reserve the rest. Lay the steaks in the marinade and flip them a few times to generously coat. Set aside to marinate for 10 minutes.
Prepare a charcoal grill for two-zone cooking and build a medium-high fire, or heat a gas grill to high.
When the coals are glowing red and covered with a fine gray ash, add your smoke source (chips, chunks, or log). Carefully wipe the preheated grill grates with a lightly oiled paper towel. Using a grill brush, scrape the grill grates clean, then carefully wipe with a lightly oiled towel again.
When the fire begins to produce a steady stream of smoke, place the steaks over direct heat, close the grill, vent the grill for smoking, and smoke for 2 minutes. Move the steak to indirect heat, close the grill, and smoke for 4 to 5 minutes. When juices appear on the top of the meat, flip the steak and repeat the whole process, starting on direct heat for 2 minutes, then moving to indirect heat for 4 to 5 minutes, until the meat is nicely charred and glossy and an instant-read thermometer inserted into the thickest part of the steak reads 125°F (52°C), 15 to 20 minutes total; carryover heat will take it to 130°F (55°C) for medium-rare as it rests. Transfer the meat to a cutting board to rest for 10 minutes.
Using a sharp knife, cut the meat off the bone, then cut the sections into thin slices. Serve with the remaining marinade on the side.