Marinate the steak by combining soy sauce, brown sugar, sesame oil, minced garlic, grated ginger, rice vinegar, and black pepper. Place the steak in a resealable bag with the marinade and refrigerate for at least 30 minutes, preferably 2 to 4 hours.
Cook the steak on a preheated grill or skillet for 4 to 5 minutes on each side for medium-rare. Let it rest for 5 minutes before slicing.
Prepare the rice by rinsing it under cold water, then combine with water or broth in a pot. Bring to a boil, then reduce heat and simmer for 15 to 20 minutes. Let it sit covered for 10 minutes before fluffing.
Assemble the bowls by placing rice at the bottom, topping with sliced steak, and adding fresh vegetables.
Add toppings like sesame seeds, chili flakes, and fresh herbs before serving.