Parboil the chestnuts. Peel the shells and inner skins neatly. 30 minutes before cooking the rice, wash the rice and let sit in a colander.
Put the rice, sake, and salt into the rice cooker. Fill with water until the appropriate water line and then place the chestnuts on top. Place the konbu seaweed on top and when it expands, cook the rice.
Once done, remove the konbu seaweed, mix it all up, and enjoy.