Boil the buckwheat noodles, rinse them in cold water, and drain well.
Slice vegetables such as cucumber, avocado, carrot, and red onion thinly.
Cut salmon (or tuna, etc.) into bite-sized pieces.
In a pan, mix soy sauce, mirin, and sesame oil to make the sauce.
Place the buckwheat noodles in a bowl and top with the prepared vegetables and salmon.
Drizzle the sauce and finish with seaweed flakes and sesame seeds.