Cut the green pepper in half lengthwise, remove seeds and pith, and slice thinly.

Drain the canned mackerel and roughly flake the fish.

Heat salad oil in a pan over medium heat, add mackerel and stir-fry. Add green pepper and stir until coated with oil. Add soy sauce and water, then simmer briefly to make the dipping sauce.

Boil a large pot of water, add soba noodles, and stir lightly to submerge. Reduce heat to maintain a gentle boil and cook according to package instructions. Rinse with cold water and drain.