Cook sago according to package instructions. Sago is cooked when it turns transparent. Drain, rinse under cold running water, then drain again. Transfer drained cooked sago to a large bowl or container.
Separate pomelo pulps and add to the bowl with sago.
Dice mango into small cubes. Transfer 1/4 of diced mango to the bowl, and transfer the rest of the mango to a blender.
Add coconut milk to blender and blend until smooth.
Transfer mango coconut milk mixture to the bowl. Stir to combine.
Let chill in the fridge for at least 2 hours before serving. Garnish with extra diced mango, pomelo pulps and coconut milk. Enjoy!