Soak the Soybeans: Soak the soybeans in 1200ml of water. The soaking time varies with water temperature: 10 hours at 25°C/77°F (summer), 20 hours at 15°C/59°F (spring, autumn), 30 hours at 5°C/41°F (winter).
Blend Soybeans: Blend the soybeans and water to make namago.
Cook Namago: Boil 1600ml water in a large pan or pot, add the namago, and stir for about 10 minutes, ensuring not to burn it.
Strain to Get Soy Milk: Turn off the heat and strain the namago with a filter cloth to get soy milk. The leftover okara can be used for making cookies.
Prepare Coagulant: Mix 20ml nigari (or lemon juice) with 50ml water to make the coagulant.
Curdle the Soy Milk: Heat up the soy milk to 75°C, add the nigari-water mix and stir gently. Do not overmix. Turn off the heat and leave it for about 10 minutes.
Shape the Tofu: Prepare a container for shaping the tofu. You can make holes in the bottom of a paper drink carton or tupperware, or use your filter cloth tied tightly to shape the tofu.