I could have sworn I had already posted a recipe for tuna soboro already, and I was all set out to call this the Much Improved version. But what do you know - I had neglected to post any recipe for this frugal bento staple at all. But no matter; this version would probably have superceded any previous versions anyway.
During my stay in Japan, one thing that I asked my mother to make for me over and over again was fish simmered in a sweet-savory broth flavored with ginger. Here’s an example - simmered komochi garei (子持ちがれい). Karei (garei) is a type of flatfish, similar to flounder or plaice (French: limande), and komochi means that it has a lot of children, or eggs. This is one of my favorite fish dishes!
This tuna soboro uses a humble can of flaky tuna and other ingredients that anyone should be able to get easily, to reproduce the flavor of sweet-salty, ginger-scented simmered fish, in around 5 minutes. No mirin or sake is used, so really anyone can make this. It is great as a rice topping, as well as an onigiri (rice ball)  filling. Mix it with some mayonnaise if you dare, for a rather unusual sandwich filling. In short, it’s a great bento staple.
Unlike the previous sakura denbu  recipe, this one is really really easy and quick. (So what’s the difference between soboro and denbu, you ask? Well, denbu is supposed to be fluffy and fine, and soboro is moister and chunkier.)
Makes 1 cup, or 2 to 4 servings, depending on how you use it. Approximately 350 calories for the whole amount.
Dump the contents of the tuna can, water and all, into a saucepan or frying pan, over medium heat. Stir the tuna around, breaking it up with chopsticks or a fork, until it’s flaky. Add the grated ginger, sugar and pineapple juice and keep stirring until the moisture is mostly gone - but don’t let it get too dry; it should be a bit moist and clumpy.
Push the tuna to one side of the pan to make an empty space on the bottom of your pan. Pour 2 tbs. soy sauce onto that empty space - it should sizzle. Mix it into the tuna. Taste, and add more soy sauce and/or sugar if you think it needs it.
Let cool. Store in an airtight container in the refrigerator, for up to 3-4 days. It can also be frozen for up to a month.