Mix together sugar, soy sauce, mirin and sake on a separate bowl.
Wrap the tofu with a kitchen towel and microwave for 3 minutes. Remove the towel and let the tofu cool down.
Slice the tofu to 6 rectangular pieces and cover with flour/corn starch. Heat the vegetable oil in a frying pan and place the tofus to grill. Once the tofus are grilled, add in the mixture from Step 2 to cook together. The Tofu steaks are now ready!