Put all the ingredients into a sauce pan. Stir over low heat without bringing it to a boil. Turn the heat off when the salt and sugar has dissolved completely.
Once the sushi vinegar has cooled enough, take out the kombu to store. You can add sugar later if it doesn't taste sweet enough.
Add 30 ml of this sushi vinegar to 1 rice cooker's cup worth of rice. Use a slotted spoon and mix in cutting motion, and let cool. For smaller portions, mix in 1 scant teaspoon for 50 g rice, and 2 scant teaspoons for 100 g rice.
To cook the best rice, use slightly less water, add 1 tablespoon sake and 1 slice of kombu.
A recipe to make storable aburaage - Recipe ID: 2087325. If you make this as well, you can make inarizushi anytime you'd want.
I made some easy chirashizushi. Recipe ID: 2105956 - For your reference!
Story Behind this Recipe
My sister, a chef, has taught me this recipe from her secret recipe book. You can store this for 2-3 months in the fridge, but the color will darken and the flavor will lose any tartness after some time. I adjusted the amounts of the ingredients to the minimum so that you can use this sushi vinegar immediately after it's done.
You must use rice vinegar for the vinegar! This adds a milder taste. Don't boil the vinegar when heating. Otherwise, it will lose any tartness and will taste horrible. An alternative without using gas: stir the ingredients well until everything has dissolved. Skim off any scum, and let sit for minimum 30 minutes to finish.