Combine the teriyaki sauce, peanut oil, lemon, garlic and ginger in a large bowl. Add the tofu, and toss till combined. Let marinate for 15 minutes.
Meanwhile, preheat a char grill pan over medium heat, and brush with oil. Cook the kumura on the preheated pan for about 3 minutes each side, or until tender. Set aside in a warm place.
Remove the tofu from the marinade. Reserve the marinade. Cook the tofu on the preheated char grill pan for about 4 minutes each side.
Cook the soba noodles (see note 3) until al dente, then drain well.
Place the reserved marinade in a small saucepan over medium heat and bring to the boil. Reduce the heat and simmer for 2 minutes.
To serve, divide the noodles between four plates. Arrange the tofu and kumura slices on top of the noodles and drizzle with the marinade.
Note 1:I think you could leave out the oil or reduce the quantity and it'd be fine.
Note 2:Or lots more if you're a ginger fetishist like me.
Note 3:The instructions on the back of soba noodle packets vary. Some tell you to just cook them in boiling water for 4 or 5 minutes and then drain. This is a big lie and will just give you disgusting gluggy soba noodles. This is how you do it: Bring a saucepan of water to the boil. Add the noodles. When they come to the boil, add one cup of cool water. Let them come to the boil again. Repeat this twice. When they come to the boil the last time, turn down the heat and cook gently till softened but still firm. Drain in a colander and rinse in cold water.
Majorly adapted from a recipe in Elle Cuisine, Autumn 2000.