oarfish
A large and elongated abyssal fish with a silvery body and red fins. Also called the "the king of herrings" or ribbonfish. The Japanese name is Ryuuguu no Tsukai, lit. "Messengers from the undersea palace of the sea dragon god."
Nagae Iku from Touhou series is an oarfish youkai.
See also
This tag implicates fish (learn more).
