Blend the boiled aduki beans and 300 ml water in a blender until the graininess is gone (roughly for 1 minute).
Strain into a large bowl.
Add 300 ml water and powdered agar into a pot. Stir and dissolve. Boil for 2 minutes over medium heat.
Turn the heat off. Add sugar, salt, and the strained mixture from step 2. Mix everything together.
Pour into a container. Chill in the fridge to harden.
Story Behind this Recipe
People eat mizu-yokan in the kotatsu back in my home town, but it's ¥600 for a box. I changed the recipe that my husband taught me. It's done in roughly 30 minutes.
Work fast in steps 4 and 5 since the agar hardens really quickly. In step 1, I took a break each time I blended for 10 seconds rather than blending for 1 whole minute. The grains (or aduki skin) will removed when you use a sieve (or a strainer) in step 2. This is a must since the texture is so different when you omit this process!