Soak the Dried Shiitake in water overnight. Cut off the Shiitake stems and thinly slice the cap.
Wash the rice and drain the water.
Add the rice, Dashi broth, water, and Shiitake to the pot.
Cook on medium heat. When it starts to boil with white bubbles, gently stir with a wooden spoon or other utensil to make sure the rice does not stick to the bottom of the pot.
Turn the heat down to very low immediately and cover with a lid, leaving a small opening as large as a chopstick. Simmer for 40 minutes. Occasionally stir with a wooden spoon.
While simmering, cut the takana mustard leaves into 5mm pieces, remove the seed from the umeboshi and cut into 3mm cubes.
After 30 minutes, the rice will start sticking to the bottom of the pot, so stir gently with a wooden spoon and adjust the amount of water according to your preferred hardness.
Turn off the fire and mix 6. in.