Cut cherry tomatoes in half, chop basil leaves, and mince garlic.

Cut the Pacific saury in half, sprinkle with salt, let sit for 5 minutes, and pat dry. Coat lightly with flour.

Mix cherry tomatoes, olive oil, mustard, salt, and pepper in a bowl to make the tomato sauce.

Heat olive oil in a pan over low heat, sauté garlic until fragrant, then add Pacific saury and cook for 3–4 minutes per side.