Chop potatoes, radish, carrot, and onion into large chunks. Slice garlic thinly.

Marinate the beef with mirin to remove any odor.

Prepare kombu broth by boiling kombu in water. Mix soy sauce, sugar, tsuyu, and mirin into the broth.

Heat oil in a pot and sauté potatoes, carrots, and radish briefly. Add the prepared broth.

Add the beef and bring the mixture to a boil.

Reduce heat to medium and add green peppers, garlic, and onion. Simmer until vegetables are tender.