Line a heatproof dish with a sheet of paper towel. Place the firm tofu and microwave for 3 minutes without covering the dish. Chop it up into 8 equal pieces that are about 1 cm thick. Coat the tofu with katakuriko.
Chop up the green onions finely.
Spread some sesame oil in a frying pan. Place the tofu inside and turn the heat on. Shake the frying pan occasionally to avoid the tofu from sticking. Toast both sides until golden brown.
Here's an example for a single serving: Align 4 pieces of tofu on a dish. Evenly sprinkle a pack of bonito flakes on top. Finish by topping with a generous amount of green onions. .