You can easily make delicious sweetened simmered fish that is soft right down to the bones by making it in a pressure cooker. Even my kids who hate eating simmered fish love this one. You can also enjoy it as a snack.
I learned this recipe from my older sister.
Make sure to wash the entrails out well. Please boil it down after removing the lid if there is a lot of liquid leftover.
Enjoy Japanese food around the world.