There's a bit of a difference. He now resides in California where the company would be required to spell out IP assignment in an employment contract. It's not uncommon for those contracts to spell out a profit sharing agreement to entice additional development. It's not uncommon for these guys to be serial inventors with many patents to their name. In some states, lack of spelling it out means the employee is free to keep the patent and the company would simple have non-transferable royalty free rights.
That's not to say inventors don't get screwed in the US, but there's at least a chance that if you keep your wits about you that you'll end up with a percentage of the royalties.
Japan has a real hard-on for the company being placed first over everything else. For instance in the entertainment business no one will book you without a talent agency. The agency takes the majority profits and more or less tells you how to live your life. Don't like it, good luck getting on TV or having your stuff produced. There's a lot of stars from the 70s through the 90s that appeared to be living nicely while they were doing well, but it ended up the company owned everything and paid for housing and transport. When they fell from fame they basically had very little money to show to years of stardom.