Combine the water and the sugar, and stir until the sugar is completely dissolved. Add the kuzu starch and mix well. You may need to sieve the liquid if the starch is still in large clumps. Pour the mixture into a medium saucepan. Place on the hob on medium heat and stir with a spatula. Once it starts to bubble, reduce the heat to medium low and stir until the mixture thickens and becomes clear, about 2-3 mins. Remove from the heat. Prepare small balls, about 30g in size, of the sweet azuki bean paste. Prepare an ice cube tray by filling it with water and then dumping it out. This will help the mixture to not stick once cooled. Pour in the kuzu mixture into the ice cube tray until half full. Place one ball of sweet bean azuki paste into each of the wells, and then pour the remaining mixture on top to seal it in. Place in the refrigerator and allow to cool for about 2 hours. To remove from the ice cube trays turn over onto a plate or clean surface. You should be able to pull them apart, but can use a knife instead. Enjoy with some kuromitsu syrup or kinako powder if desired for a delicious summertime treat.