1. For dressing, in a small bowl, add wasabi, soy sauce, mirin, and sugar. Mix well.
2. In a large saucepan, boil water with salt. Drop noodles in boiling salted water and cook for 2 minutes or until tender.
3. Drain, and rinse noodles in cold water.
4. In a large mixing bowl, drop rinsed noodles. Pour sesame oil, and toss well.
5. In a separate bowl, combine sansho, oil, and salt. Mix well. Brush mixture on both sides on salmon. Set aside.
6. Place a large saucepan on medium flame, pour oil, and add salmon in it. Cook each side for 2-3 minutes or until desired doneness. Baste salmon with oil mixture while cooking.
7. Transfer fish over noodles, and flake using a fork.
8. Sprinkle spring onion, coriander, cucumber, and half of the dressing. Toss well.
9. Transfer it to a serving platter, drizzle with remaining dressing and serve immediately.