Cook the tapioca pearls:

1. In a medium saucepan, add 6 cups of water and bring it to a boil over medium-high heat.
2. Add tapioca pearls and turn the heat down to medium-low. Cook for 15-20 minutes, stirring occasionally to prevent from sticking to the bottom of the pan. The pearls will turn translucent, but at this point, you might still see a tiny white dot in each pearl.
3. Turn off the heat and let the pearls rest in the hot water until all the tapioca pearls become completely transparent, about 15-20 minutes.
4. Rinse the pearls under running water to cool off and drain in a fine mesh sieve or colander. Set aside.

Prepare the mango sago:

1. Slice each mango in half away from the pit and use a large spoon to scoop out the flesh. Set aside 1/4 cup flesh (about half a mango) and dice into cubes to use as a topping.
2. Add mango, coconut milk, and condensed milk in a blender. If you like your sago cold, add 3-4 ice cubes in the blender. Blend until smooth, about 1-2 minutes.
3. Divide the mango mixture into bowls. Stir in tapioca pearls and top with cubed mango.