Slice the onion thinly. Separate celery leaves from stalk and cut the stalk into thin diagonal slices. Cut the leaves into bite-sized pieces. Trim the root of shimeji mushrooms and separate them. Slice garlic thinly after removing the core.

Season the beef with salt and pepper.

Heat olive oil and garlic in a pan over low heat until fragrant. Add onion and sauté over medium heat until softened. Add beef and cook until the color changes, then add shimeji mushrooms and celery stalks. Stir until coated with oil.

Add water, canned tomatoes, and additional seasonings. Mix well and bring to a boil. Add celery leaves, mix, cover, and simmer on low heat for 7–8 minutes.