Place steak in a single layer in a 13 x 9-inch glass baking dish. Whisk 1/3 cup soy sauce, 2 Tbsp. sugar, 1 Tbsp. sesame oil and black pepper together in a small bowl. Pour half (1/4 cup) of the marinade over the steak and flip the steak to coat; set aside. Set aside the remaining marinade to drizzle onto the finished steak.

Whisk rice vinegar, remaining 1 Tbsp. soy sauce, remaining 1 tsp. sugar and remaining 2 tsp. sesame oil in a large bowl until the sugar is dissolved; add corn, cabbage and cilantro and toss to combine; set aside, tossing occasionally.

Heat oil in a large skillet over medium-high heat. Pat steak dry with paper towels and discard the marinade in the dish. Add steak to skillet in a single layer (it's okay if the pan is crowded). Sear, adjusting heat as needed, 3 to 5 minutes on each side, until browned and the thickest piece registers 120°F to 125°F for medium-rare steak. (Or cook to 130°F to 135°F for medium steak, and 140°F to 145°F for medium-well steak — add a minute or two for every 10 degrees needed.)

Transfer steak to a cutting board and set aside to rest 5 minutes. Meanwhile, warm tortillas. Slice steak thinly across the grain, transfer to serving dish, and drizzle with the reserved marinade. Serve steak in tortillas with slaw, radishes and garlic chili sauce. Can fill lettuce leaves instead of tortillas.