Trim the shimeji mushrooms, slice the onion thinly, and mince the garlic after removing its core.

Cut the swordfish into bite-sized pieces, pat dry, season with salt and pepper, and coat lightly with cornstarch.

Heat olive oil in a pan over medium heat and cook the swordfish until golden brown on all sides. Remove and set aside.

In the same pan, sauté garlic, shimeji mushrooms, and onion over medium heat until softened.

Add the diced tomatoes, sugar, salt, consomme powder, and water. Bring to a boil, then cover and simmer over low-medium heat for 5 minutes.

Return the swordfish to the pan, cover, and simmer for another 3 minutes. Remove the lid and cook until the sauce thickens.