This is SHARK!
As I mentioned before, oden is a popular dish in Japan in the wintertime. It has a variety of ingredients, which vary depending on areas and houses.
The triangle white things are called “hanpen”, and made from a fish paste of pollack and SHARK. Despite its dangerous origin, hanpen has a very soft and fluffy texture. It is tasteless by itself but good for oden as it absorbs the fish broth like a sponge. It’s recommended to eat hot mustard with it. It is also fun to see that hanpen become three times as big because of it absorbs liquid when you put it into the oden broth.