Put the water and agar into a pot and bring to a boil.
Remove from heat and add salt and koshi-an. Let sit to cool.
Once the mixture cools down, stir and pour into a mold, then chill in the refrigerator.
Story Behind this Recipe
I had a craving for mizu-yokan, so I came up with my own version.
The result is a very soft texture, so if you pour the mixture into the mold while it's still hot, the anko will settle to the bottom. Since it's troublesome to chill it over ice, I allow it to cool down, then stir it, and it comes out fine. If you prefer a bolder salt taste, add one more pinch.