In a bowl, mix bread flour, green tea powder, sugar, and salt.
Dissolve yeast in milk, pour it into the bowl, and knead the dough.
Add butter and knead until the dough becomes smooth.
Place the dough in a bowl and let it rise (first fermentation) for about 1 hour.
Shape the dough into a round ball and place it on a baking pan.
After the second fermentation (about 30 minutes), brush the top with milk.
Bake in a preheated oven at 180°C (356°F) for 20 minutes.