Soak the konbu in water for 30 minutes until softened. Strain the soaking water through a paper towel-lined sieve and reserve. Cut the konbu into 15cm wide strips.

Wash the kanpyo briefly, soak in water for 3 minutes, and drain. Rub with salt, rinse, and drain again.

Roll the konbu loosely from one end. Wrap the kanpyo around the center of the roll twice, leaving extra for tying. Cut off the excess kanpyo.

Place the konbu rolls in a pot without overlapping. Add the reserved konbu soaking water, sake, and vinegar. Cover with a drop lid and bring to a boil over high heat. Reduce to low heat and simmer for 30 minutes until softened.

Add the seasoning ingredients (mirin, sugar, soy sauce) to the pot. Cover with a drop lid and simmer on low heat for 15 minutes.