Yes, the Kelly Loves bento box is designed to reheat precooked foods. This is really handy, because you don’t need to transfer the food to another vessel to microwave it when you’re removing it from a fridge or lunch bag. It’s also useful if you’ve brought food into the office to reheat.
But remember: don’t ever use a bento box to cook food in a microwave oven; it’s just for reheating. And never use a bento box in a conventional oven (even on a low heat).