Make the marinade: Combine the marinade ingredients, mix well, and place in a non-reactive dish. Place the chicken breast into the marinade, turning it over to make sure it's coated on both sides. Cover and refrigerate for 4 hours.
Drop the bean threads into the hot water. Stir and let sit for 10 minutes or until the noodles are "glassy" and soft. Drain, run under cold water, and reserve. Make the dressing: In a small bowl, mix together the wasabi powder, and 1 tablespoon of water. Let sit 5 minutes. Add the rice wine vinegar, soy sauce, sugar, and sesame oil. Mix well.
Thinly slice the chicken breast. Toss together the noodles, chicken, asparagus, cucumbers, and the dressing. Place a nest of spinach on a salad plate. Make a small amount of noodle salad in the center of the spinach. Garnish with green onions.