Combine rice and water in a pot. Bring to a boil, then lower heat and simmer 15–18 minutes until water is absorbed.

Stir coconut milk, sugar, and salt in a small saucepan over low heat until sugar dissolves. Do not boil.

Mix half the coconut sauce into the hot rice. Cover and let sit 10 minutes so rice soaks.

Spoon rice into small cups. Top with mango slices and drizzle remaining coconut sauce.

Chill at least 30 minutes. Sprinkle sesame seeds before serving.