In a saucepan, bring the water to a boil. Stir in the blueberries, cinnamon, sugar, and ginger. Boil for three minutes.

Reduce the heat to a low simmer and cook for another 10 minutes, stirring occasionally. Remove the saucepan from the heat and let sit for another 10 minutes.

Stir in the plain yogurt and puree in a blender or use an immersion blender. Once the soup is smooth, chill for at least 20 minutes before serving.