Toyota Motor Vehicles (トヨタ自動車), which is what most Americans think of when they think of Toyota, is one of the members of the Toyota Group, which used to be a keiretsu, basically a related family of companies in different verticals. (Toyota is distinct from many Japanese keiretsu in that it is largely concentrated in one vertical.)

There are other big components: Toyota Industries (豊田自動織機) for example, which makes machine tools. Number one customer: well, duh. But they also sell them all to other folks as well.

Now here's where it gets hairy: Toyota Industries owns Toyota Motors (largest single shareholder), but Toyota Motors also owns a quarter of the stock of Toyota Industries.

Now repeat that with another dozen or so major companies which you probably haven't heard of, and any number of minor satellite firms.

This ends up as one big web, which is collectively the Toyota Group. It is very possible for the group as a whole to be prospering while one or several group companies struggle. How they work this out is an exercise in business management and accounting that would boil your brains -- don't ask me, I'm just an engineer (and, er, customer and shareholder and not-quite-employee but as I mentioned disentangling Nagoya from Toyota is like asking for a human body minus all the carbon).