Grind ½ tbsp dashi granules, 1 tsp bonito flakes (katsuobushi), ½ tsp salt, and ½ tsp sugar together using a mortar and pestle.
Pour the mixture into a small bowl and add ½ tsp matcha powder. Mix until combined.
Right before you use it, add 1 tbsp arare (or a crunchy substitute), 1 tbsp kizami nori (shredded nori), and 1 tbsp toasted white sesame seeds and mix until evenly distributed.
Divide 250 g cooked Japanese short-grain rice between serving bowls. Spoon the ochazuke mixture over the top.
Prepare 250 ml freshly boiled water and pour it down the side of each bowl rather than directly on top.