Add the olive oil and garlic to a frying pan and stir fry (low–medium heat) until brown to add aroma to the oil.
Turn off the heat (so that the tomato juices don't splash) and add the cherry tomatoes and Shiitake. Then, turn the heat back on.
Once the tomatoes are soft, add 1 ladle full of pasta water and stir while mashing the tomatoes.
Once the tomato starts to form a sauce, add the cooked pasta and another 1/2 ladle of pasta water and mix well.
Finally, add 1 tsp of soy sauce, 2/3 of the chopped Shiso leaves, and mix well.
Plate it up, garnish with 1/3 of the chopped Shiso leaves, and serve.