Wash and strain the adzuki beans. In a large pot, add adzuki beans and pour water until 1 inch above the beans. Bring it to a boil over medium-high heat for 5 minutes. Drain the beans and discard the water.

Return the beans to the pot with 4-5 cups of fresh water. Cover, and simmer over medium-low heat until the beans are soft and easily breakable for about 1 to 1 1/2 hours. Check occasionally to check if the soup needs more water. Turn off the heat, and let it cool for about 20 minutes.

Strain the beans. Do not throw away the drained water. Puree the beans with a hand blender or food processor. You may add a little bit of bean water if the puree is too thick.

Pour the puree over a coarse strainer over a large bowl until hard beans and skins remain in the strainer for smooth red bean soup. (optional)

Put the bean puree back into the pot. Add 1/4-1/2 cup of bean water into the puree to adjust the consistency. You may add water if you do not have enough bean water. Add sugar into the mixture and cook until boil.

In a medium bowl, add glutinous rice flour. Add warm little by a little while kneading until the dough comes together. You may need to add more or less water.

Shape the dough into 1/2-inch small balls. Sprinkle some glutinous rice flour over them so they do not stick together.

In a medium pot, boil water and add the glutinous rice balls. Cook until they float to the top. Scoop them out with a wire ladle and put them immediately into the bowl of the cold water bath to stop the cooking process.

Scoop the cooked glutinous rice balls into the red bean soup. Best serve warm.