Add boiling water to a large measuring glass or glass bowl.
Add the green tea bags and let them steep for 5 minutes. Mix in the sweetener until dissolved.
Chill in the refrigerator while preparing the peaches.
Purée the peaches in a blender or food processor. Strain the peach purée to make it smoother. It should equal about 1 to 1.5 cups peach juice. (You could also simply juice the chopped peaches if you have a juicer.)
Pour the peach juice and green tea into a pitcher and stir.
Refrigerate until chilled, at least 1 hour.
Serve in glasses over ice and garnish with peach slices and mint leaves.