The Common Sea Squirt, very often called Sea Cucumber is neither a coral, seaweed, shellfish or whatever.
It is an animal of its own class.
In its natural habitat, already a prey to many marine predators, it has become rare because of the extensive catch by humans.
Its natural colour is whitish out of the water while (see pic above) Hoya rasied by humans are of a deep orange colour.
We are just in the middle of its season, May.
They are mainly raised in Miyagi Prefecture while natural ones are caught in Iwate Prefecture.
You have to cut it open to reach its edible part.
It can be eaten raw, slightly boiled or pickled.
It is said to be the rare sea animal combining the four tastes: sweetness, saltiness, sourness and acidity.
For a better view of its insides.
It is called sea squirt, because it is mainly filled with sea water which can be expelled at will.
I personally appreciate it as sushi nigiri, although it is a bit of an acquired taste!