Bring 960 ml of water to a rolling boil in a medium saucepan over medium-high heat. Stir in the tapioca pearls immediately to ensure they do not clump or settle at the bottom.

Cook the sago at a gentle boil for 10 minutes, stirring occasionally. Remove the pot from heat, cover tightly with a lid, and let it stand undisturbed for 10 minutes until the pearls turn fully translucent.

Pour the cooked tapioca through a fine-mesh strainer and rinse thoroughly under cold running water to wash away residual starch. Drain well.

Set aside one-third of the diced mango for topping. Place the remaining two-thirds of mango into a blender along with the chilled coconut milk, evaporated milk, and sweetened condensed milk. Blend until silky smooth.

In a mixing bowl or large serving bowl, combine the blended mango coconut puree with the drained tapioca pearls. Stir gently with a spoon until evenly distributed.

Ladle into dessert bowls or glasses, top with the reserved fresh diced mango cubes, and chill in the refrigerator for at least 30 minutes before serving cold.