Soak the hijiki in plenty of water for 20 minutes so the dirt and sand floats out. It will expand four times in size, so be sure to use enough water. Drain through a sieve.
Slice the carrot into small strips.
Put the age in a sieve. Pour boiling water over it. Drain the water and cut it in half lengthways. Slice into strips.
Mix the soup stock, soy sauce, sake and mirin in a bowl.
Heat 1 tbsp sesame oil in a frying pan over a medium heat and saute the items from steps 1, 2 & 3. When the water evapourates and the oil has seeped in, add the mixed sauce from step 4 and soy beans. Simmer for 12 minutes and stir occasionally until most of the liquid is gone.