Stir agar powder in water and let sit for at least 5 minutes at room temperature.
Heat the water-agar mixture on medium-high heat, until it becomes thick and bubbly.
Stir in the white sugar and corn syrup and boil for another minute.
Lower the heat to low-medium, then add in the bean paste.
Heat the mixture over low heat for 10-15 minutes, stirring constantly.
Pour the mixture into a clean pyrex glass or silcone molds.
(optional) Stir in cooked whole red beans.
Set aside and let cool for about 2-3 hours until the middle is set.