In a medium bowl, combine sugar and matcha, and whisk. Add 2 eggs and whisk until smooth. In a small bowl, mix gelatin and water, and let sit for 5 minutes, while the gelatin blooms.
Heat milk until it boils. Immediately add the hot milk to the egg mixture little by little. Add bloomed gelatin, then let sit until the gelatin dissolves. Strain through a mesh strainer. Divide the mixture into 4 glass cups or any kind of molds. Chill in the fridge for at least 3 to 4 hours until set.
In a small pot, mix 3 Tbsp sugar and 2 Tbsp water for Matcha syrup and bring to a boil. Cook until it's reduce to half and remove from heat. Mix matcha and 2 tsp water and add to the syrup. Strain and let cool to room temperature.
Pour the mathca sauce over cold Purin before serving.