Rinse the sushi rice under cold water until the water runs clear.

In a pot, combine the rinsed rice and water. Bring to a boil over medium heat.

Reduce heat to low, cover, and simmer for 15 minutes until the rice is cooked.

In a separate pot, heat the coconut milk, sugar, and cornstarch over medium heat until thickened.

Pour the coconut milk mixture over the cooked rice and mix well.

Peel and slice the ripe mango.

Serve the sticky rice with mango slices on top.