The black arrowhead tuber (Kuro Kuwai or Karasu-imo) used in Chinese cooking is a big black arrowhead in the Cyperaceae family and is a different variety of plant from the Japanese arrowhead, and is available in cans as water-boiled arrowhead, however there is evidence that this has also been used as a food from ancient times in Japan and has been unearthed from Jomon Period remains in Kameoka, Aomori Prefecture.
中国料理に使用される黒クワイ（烏芋）はカヤツリグサ科のオオクログワイという日本のクワイとは別種の植物で、水煮の缶詰でも出回るが、日本でも古くから食用としていた形跡があり、青森県亀岡の縄文時代遺跡から出土している。