Slice the shishito peppers diagonally and mince the garlic.

Bring a pot of water to a boil, add a pinch of salt, and cook the spaghetti 1 minute less than the package instructions. Reserve 2 tbsp of the pasta water and drain the rest.

Heat olive oil and garlic in a frying pan over medium heat. Add the shishito peppers, shirasu, and red chili flakes, and lightly sauté. Season with salt and pepper.