Add dashi, soy sauce, mirin, and sugar into a saucepan and bring to a boil, stirring to ensure the sauce is well combined. Set aside to cool, or place in the fridge/freezer to speed up the process.
Cook noodles according to package instructions. Drain and rinse the noodles under ice-cold water tossing them to cool evenly, and drain them of excess water. Garnish your noodles with shredded nori, sesame seeds, and/or microgreens as desired.
Pour the dipping sauce into a small bowl and dress to your liking. Dip your noodles in the sauce and enjoy!