Isonade is an enormous, shark

Shark

Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

-like sea monster said to live off the coast of Matsuura

Matsuura

Matsuura is a Japanese name, and can refer to:Companies:*Matsuura Machinery, an international heavy machinery manufacturing company in Fukui, Fukui Prefecture, Japan*Matsuura Railway, a railway company in Nagasaki and Saga Prefecture in Japan...

 and other places in Western Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

. When it appears, fierce winds blow.

Its body has never been seen, as it is always hidden beneath the waves, save for its huge tail fin which is covered in small barbs. It approaches boats stealthily and uses its hooked tail to snare sailors and drag them into the sea, where it devours them.

It may also simply use its tail to capsize boats, or strike the beach with its tail and kill people there.