This is how to skin a Japanese squid. It's the same method that I introduced in my recipe for Fermented First-Rate Japanese Squid (Recipe ID: 127834), but since it can be used in other recipes, I'm posting it separately.
To begin, remove the squid's tentacles and internal organs, and remove the cartilage in its back.
To tear off the squid's fins: To do this, use your hands to peel the fin from the base to the top in a straight and quick motion, continuing to the tip of the squid. It's easy to tear the meat at the base of the fin, so be careful! The idea is to just peel off the skin.
Grasp the part of the skin that has already peeled back, and pull it up. Place the squid with the skinned side down on a cutting board, and gently peel off the skin from the bottom to the top.
Each squid will be different, and some will be easier to skin than others, but peeling from bottom to top works well.
No matter what you do, there will still be some skin remaining at the opening of the body, so slice about 5 mm off of the ends. You can use this piece, along with the fin and tentacles, in other recipes.
You can use the skinned torso for sashimi, fermenting, stir-frying, etc. Skinned squid looks better in stir-fried dishes.
Story Behind this Recipe
There are a surprising amount of people who have trouble with skinning squid, so I decided to post this.
Squid are slippery, so it helps to use paper towels or cotton gloves. Rinse the squid as little as possible with water to prevent it from getting cloudy. Rinsing also affects the taste, so the less the better. If preparing sashimi, scrub the squid with a paper towel to remove the thin skin to make it taste even better. If you're making raw squid noodles, slice it in half horizontally, and then vertically julienne the squid to get tender pieces.