Transfer the kombu into a saucepan and also add the mirin and the rice vinegar. Then bring this to a simmer on a medium heat. After that turn of the heat and add the bonito flakes. Then let it marinade for 10 minutes. Once that’s done pass it through a fine sieve and season it with the lime juice and the soy sauce. Mix it well and let it marinade in your fridge for at least 30 minutes.