I don't know exactly where to begin, there are so many various experiences out there.
However, if you're young and inexperienced, you'll start at the bottom.
(You said late twenties, fresh start = So that makes you young and inexperienced.)
Admittedly, I also have the problem of not having a deep view of other industries.
I know my own pretty well and you don't really make money above the average unless you've got experience with a title.
If I were you, starting over, I'd take a good hard look to see what's in demand.
Is there a niche you can fill for someone?
(Anything in IT is a death sentence in Japan unless you're a consultant or a higher-up manager, director or project leader.)
Business... anything in Insurance, Financial, Compliance, Medical, Research, Legal and probably some Media can be a good start to something more long term in an industry that will always have a need for professionals. With N2, you shouldn't have much problem getting into some of the Japanese firms spreading their wings into new markets or even those that have existing markets outside of Japan.
I do recommend a mixed firm that may be Japanese based but has connections to global offices; The outside influence sometimes makes the J-office life more bearable.
Going into strictly Japanese firm without any western influence will drive you mental, if you can't adapt to their ways.
I'm really tired of listening to other foreigners gripe about going to work for a Japanese company and then getting fired because they couldn't follow the rules. Or, can't get along with co-workers because they refuse to adapt and instead, try to force everyone else to change for them.
Ummm so back to the topic...
A entry level position with a mixed firm could net you 4-5m if it's a professional outfit (meaning, legal, finance, etc.). Less, probably, if it's just an average company.
I slid into a professional role here in Japan and eventually created my own market once I was given a greenlight to do so. I had a large amount of experience beforehand though. (But, spoke zero Japanese at the start.
)
Hell, I know a dude that comes to Japan, buys used cars and exports them out and makes a shit ton of money doing it. There's always something, it's just a matter of what effort you're willing to put into it.