In a shallow baking dish (8 X 8-inch is perfect), combine the tangerine juice, Mirin, Tamari and chili paste. Set aside.
Drain the tofu and cut in into 2-inch squares, about ½-inch thick. Place them in the marinade, turning them to quickly coat both sides. Cover with plastic and marinate for 30 minutes at room temperature. Then flip each tofu square over and marinate for another 30 minutes.
Preheat a stove-top grill, remove the tofu from the marinade, place it on a large plate and drizzle or brush it lightly with grape seed oil. (Save the marinade!)
Once the grill is hot, put the tofu squares on, at least an inch apart. If you don't hear the sizzling sound, wait until you do, or your tofu will not brown and caramelize. Cook each side until nicely marked, about 2 minutes each.
In a small sauté pan, bring the marinade to a boil and then reduce it to a simmer for about 5 minutes. Pour this over the tofu when it's done.