Firefly squid is a common food at Japanese eating places such as Japanese sushi / restaurants / bars (called IZAKAYA). It is known as the sparking squid in the ocean.
I sometimes eat it. It is called ホタルイカ（ほたるいか）Hotaruika in Japanese.
Hotaru means firefly. Ika means squid.
The dishes as shown in this page cost usually from 100 to 300 yen.
It is usually eaten boiled, marinated or raw.
Boiled Firefly Squid
Boiled fire fly squid is popular and easy to find at supermarkets, Japanese restaurants and bars in Japan.
Vinegared miso is good sauce for boiled firefly squid.
Putting soy sauce and ginger is also good.
This is boiled firefly sushi.
Marinated Firefly Squid
This is a cooking method called 沖付け Okizuke that means marinating really fresh squid or fish in soy sauce and some seasonings.
Marinated Firefly Squid Sushi
Sashimi Firefly Squid
Sashimi (raw) firefly squid is rare and difficult to find at eating places because distributing it fresh is very costly.
It is called...
Dried Firefly Squid
A pack of domestically produced (日本海産) dried firefly squid is only 100 yen. (108 yen including tax) This is really cost effective.
It is sold at a convenience store LAWSON STORE 100.
6 pieces are in the pack.
Some sake bars offer this as well.
It is served with lighter at some bars. You can cook yourself.
Sake and Firefly Squid
By the way. My favorite squid restaurant is this.
How about mini octopus?