Wash azuki beans and drain. Add beans to a pot with 2½ cups water. Boil for 20 to 30 minutes. Drain the beans but reserve cooking liquid and allow it to cool.
Cover beans with plastic wrap so that the beans do not dry out.
Wash glutinous rice and white rice until water runs clear. Drain rice.
Combine rice and beans in the rice cooker, along with ¼ teaspoon table salt and reserved cooking liquid.
Add additional water according to your rice cooker's measurements to make 3 cups water and steam the rice with the azuki beans.
Meanwhile, make "gomashio" by combining roasted black sesame seeds and salt. Set this aside.
NOTE: Black sesame seeds can be purchased roasted. If they are raw, just heat the sesame seeds in a dry pan for about 3 to 5 minutes, continuously shaking the pan or stirring the sesame seeds so that they don't burn.
Once the rice is cooked, serve osekihan in individual rice bowls and garnish with the black sesame seed and salt mixture.
Notes
Adapted from Just Hungry.com
Recipe by Bebe Love Okazu at https://bebeloveokazu.com/2012/10/22/osekihan/