In a medium saucepan, combine blueberries, water, raw sugar, and fresh lemon juice. Bring to a boil over medium heat, stirring occasionally. Once boiling, reduce to a simmer for 5 minutes, then strain and set aside to cool.

While the blueberry juice cools, boil water in a kettle. After boiling, let it cool slightly to around 170-180°F. Place green tea bags in a heatproof pitcher and pour hot water over them. Steep for 3 minutes, then remove the tea bags.

In the saucepan, combine the cooled blueberry juice with the brewed green tea. Add the juice of half a lemon and stir gently.

Chill the Blueberry-Lemon Green Tea in the refrigerator for at least 30 minutes, or pour over ice. Serve in glasses garnished with fresh blueberries and lemon slices.