Soak the lima beans overnight so that they expand by 3-5 times their size.
In a pot, heat the beans and water and once the water has come to a boil, discard. Pour fresh water into a pot and bring to a boil.
Discard the boiled water, transfer the cooked beans to a bowlful of fresh water and peel the membrane of each bean.
Boil the peeled beans with water again and skim off the scum periodically until the beans become crumbly.
Mince the sakura leaves. Mix the red rice yeast with a tiny amount of water into a paste.
Purée the beans in a food processor, then cook the beans with a third of the amount of sugar.
Add the water-dissolved red rice yeast, then the remaining sugar. Cook down.
Once the water has evaporated and the mixture has hardened, add the minced sakura leaves and turn off the heat. Let cool.
Story Behind this Recipe
I settled on this procedure to simplify the labor-intensive sakura an paste.
I used to make this with preserved sakura blossoms, but the end result was too tart and bitter, so I now use salt-preserved sakura leaves. Even if you don't pass the beans through a strainer, it'll have a smooth texture from blending in a food processor.