Tatsuta-age is fish or meat marinaded in soy sauce, mirin, ginger and the like to remove its smell, then coated in katakuriko (starch of dogtooth violet) and deep-fried.
The name "Tatsuta-age" comes from the Tatsuta-gawa River, a famous river for viewing colorful autumn leaves that flows through Ikaruga. It is said that this dish was so named because the soy sauce turns red when it is deep-fried, and the sight of the white katakuriko standing in relief against it here and there resembles autumn leaves flowing down the Tatsuta-gawa River.
Another theory holds that the head cook on the light cruiser Tatsuta in the Imperial Japanese Navy used katakuriko as a substitute for flour when making deep-fried fish or meat. However, the ship name Tatsuta comes from the Tatsuta-gawa River, so whichever story you believe, Tatsuta-age has a deep connection to Ikaruga-cho.