Handy frozen food for lunch box.

In Japan, we have frozen food specificly designed for lunch box.
You can find so many kinds so that you don't get bored of your daily lunch and they are separeted in a small portion to fit in lunch boxes. Most of the frozen food needs to be heated in a microwave before placing into a lunch box but some don't. You just place the frozen food into a lunch box and by the time you eat it, it will be defrosted naturally.
If you see it in a supermarket, it's worth trying!