The prevalence of bonito flakes and niboshi may seem daunting to vegans. But not to worry. In Japan's Buddhist cuisine, vegetarian dashi can be made from a variety of dried vegetables. The most popular example is a combination of konbu and dried shiitake mushrooms, both of which are super rich in umami. Konbu, an important part of ichiban-dashi, can also be used on its own and is a perfect match for tofu dishes.
Japanese dashi is best used on the day it's made, but if you have some left over then put it in an airtight container. It will keep in the refrigerator for a couple of days. Another approach is to make a big batch and freeze it, which is what a lot of Japanese cooks do.