Combine all but sesame seeds and salmon in a saucepan. Bring to boil and slowly simmer until a syrupy consistency is achieved, about a 50 percent reduction. Let cool completely.
Add sesame seeds and salmon and marinate for 1 hour. Remove salmon from marinade and bring sauce to a boil. On a hot grill, cook salmon for about 3 to 5 minutes per side. Occasionally, brush the salmon with the teriyaki sauce.
MIRIN CUCUMBER SALAD: Make a paste with the wasabi and mirin. Whisk in vinegar and sugar. Whisk in oil. Season with salt and pepper. Toss the cucumbers with enough vinaigrette to coat completely. Lay grilled salmon on top of small pile of salad. Garnish with sesame seeds.