Chop the umeboshi and shiso finely. Cut the sliced cheese into 1cm squares.
Combine bonito flakes with the soy sauce and mix well. Add all the other ingredients and mix together thoroughly.
Here's a variation coated with bonito flakes, inspired by a recipe (Recipe ID: 1503877) by user "Edamame-korosuke." This one's good too.
Story Behind this Recipe
My family loves the combination of shiso and cheese.
Please adjust the amount of ingredients to your liking. I approximated the amount of rice by 4 breakfast servings (2 rice balls each). If you're halving the recipe, toss the whole package of bonito flakes, because it tastes delicious when there's lots. You can add edamame to make it colorful.