Rinse the red beans thoroughly and soak them in water.
Add the soaked red beans to a pot and boil until cooked.
Strain the cooked beans to leave only the red bean paste.
Add sugar, salt, agar powder, and water to the red bean paste and mix well.
Simmer over medium heat in the pot, stirring consistently.
Once the mixture thickens, turn off the heat and pour it into a mold to cool.
When fully set, cut into bite-sized pieces.