Heat Japanese plum wine (red or white) and sugar in a medium saucepan over medium-high heat, stirring, until the sugar dissolves.

Add the halved and pitted plums and split vanilla bean and simmer until the plums are just tender, about 5 minutes.

Transfer the plums to a plate using a slotted spoon, reserving the poaching liquid.

Peel the plums, if desired, and slice into thin wedges.

Sprinkle the unflavored gelatin powder over 1/2 cup cold water in a small bowl.

Let sit for 1 minute to bloom the gelatin.

Stir the bloomed gelatin into the warm poaching liquid until the gelatin dissolves completely.

Pour the mixture through a fine-mesh sieve into a bowl to remove any solids.

Let the gelatin mixture cool to room temperature.

Spray three 3-by-5-inch loaf pans or 8-ounce bowls with cooking spray, wiping out the excess.

Pour a 1/4-inch layer of the gelatin mixture into each mold.

Refrigerate until firm, about 20 minutes.

Arrange half of the plum slices on top of the firm gelatin layer in each mold.

Add just enough of the gelatin mixture to cover the fruit, then return to the refrigerator until firm, about 20 minutes.

Repeat the layering process to make another gelatin layer and another fruit layer.

Fill the molds with the remaining gelatin mixture.

Refrigerate until fully set, at least 3 hours or overnight.

Unmold the gelatin: Bring 2 inches of water to a simmer in a wide saucepan.

Run a butter knife or small offset spatula around the top edge of the gelatin to loosen it.

Dip the bottom of each mold into the hot water for about 10 seconds to help release the gelatin.

Invert the molds onto plates to unmold the gelatin.