Tenkasu (天かす, lit. “tempura refuse”) are crunchy bits of deep fried flour-batter used in Japanese cuisine for example in soba, udon, takoyaki and okonomiyaki. Hot plain soba and udon added tenkasu are called tanuki-soba and tanuki-udon (haikara-soba and haikara-udon in Kansai region).
It is also called agedama (揚げ玉, lit. “fried ball”). Tenkasu is more common in western Japan and agedama is more common in eastern Japan.