Kitsune udon is thick udon noodles in a clear dashi broth topped with sweetened aburaage (thin-fried tofu). The aburaage is simmered separately in soy sauce, mirin, sugar, and dashi until it absorbs the braising liquid and becomes sweet and yielding.
Regional broth difference
Kansai (Osaka) broth is pale, made with kombu-heavy dashi, lightly salted. Kanto (Tokyo) broth is darker, uses more katsuobushi and more soy sauce, and reads saltier. The same dish in Kyoto and Osaka looks quite different from the version served in Tokyo.
Aburaage prep
Pour boiling water over fresh aburaage to remove excess oil before simmering in seasoning. The pouch should plump slightly as it absorbs broth.