The Japanese soup stock made from kombu and bonito flakes is called dashi.
Dashi is a family of Japanese stocks, with the classic version made by steeping kombu, an edible kelp, and katsuobushi, dried and fermented bonito flakes, in water. The liquid is strained before use. This combination supplies glutamic acid from the kombu and sodium inosinate from the bonito, creating a powerful umami synergy.
Dashi is not the same as miso, soy sauce, or mirin. Miso is a fermented soybean seasoning, soy sauce is a salty fermented condiment, and mirin is a sweet rice wine used in cooking. Dashi is the savory liquid base that may carry those flavors. It is fundamental to miso soup, clear soups, noodle broths, simmered dishes, okonomiyaki, and takoyaki.
There are several versions. Kombu-only dashi is vegetarian, while niboshi dashi uses dried sardines and shiitake dashi uses dried mushrooms. Instant granules and liquid concentrates became widespread in Japan during the second half of the 20th century, making homemade stock less universal than it once was.