Sprinkle the agar powder over 500 ml water in a 2-quart / 2 L saucepan. Let it sit for 5 minutes to bloom.

Bring to a boil over medium heat, stirring often. Once boiling, lower the heat and simmer for 1 to 2 minutes, stirring, until no agar grains remain on the spoon.

Stir in the sugar until dissolved, then pour into a 20 cm / 8-inch square dish. Cool at room temperature for 20 minutes, then chill for at least 1 hour until firm and cuttable.

Run a wet knife around the edge and cut the jelly into roughly 2 cm cubes.

Put the shiratamako in a mixing bowl. Add water a little at a time, kneading, until the dough feels soft like an earlobe and holds together without cracking.

Divide into 12 pieces, roll into balls, and press a shallow dimple in the center of each with your thumb.

Bring a pot of water to a boil and drop in the dango. Boil until they float to the surface, about 2 to 3 minutes, then let them bob for 1 more minute. Scoop out with a slotted spoon and drop straight into a bowl of ice water.

Combine the dark brown sugar and 50 ml water in a small saucepan. Simmer over low heat for 3 to 4 minutes, stirring, until glossy and slightly thickened. Cool before using.

Divide the kanten cubes among 4 bowls. Add 3 dango, a scoop of anko, and a mix of mandarin, strawberry, and pineapple to each bowl.

Add a scoop of ice cream if using, then drizzle each bowl generously with the cooled kuromitsu syrup right before serving.