A company can sponsor an IT worker quite easily. The recipient needs to have a degree or 10 years of experience (though degree is strongly preferred due to paperwork) and can’t have a criminal record (to simplify a bit).
They (employee being hired) should be prepared to make 1/4 to about 1/2 what they would make in the US, almost certainly have full in-person office time, and the exchange rate to USD is the worst it’s been in over 30 years with no sign of recovery (my salary converted to USD is worse now than when I made far less gross salary), etc.
In the case of Americans, the added bonus that the Japanese versions of retirement accounts (iDECO and NISA) are basically off-limits because the IRS taxes them punitively. Several investments are off limits for the same reason (PFICs). They can’t contribute to a 401k unless they have US taxable income which would mean double taxation. If they make over the IRS’s minimum (which is hard with a Japanese salary and exchange rate at the moment outside of FANG and certain fintech), they do get the pleasure of being double-taxed. Either way, they still have to file US taxes every year and likely FBAR as well.
Oh, and if they want to work for any of the major game studios, they will need to read, write, and speak a certain degree of Japanese.
Few banks, medical institutions, etc. have much if any English support (though it is getting better).
If they like weed or anything, it’s still super illegal here and will result in detention for up to 23 days before charging, serving a jail sentence, and being banned for anywhere from 5 years to life from Japan. This could also happen if their family/doctor in the US happens to send them a medication they can’t get here (for example, many types of ADHD drugs are fully illegal here).
Edit: another one! If they want to keep voting, they may need to pay state taxes as well enough if they do not live there and will not set foot there again; it depends upon the state how that is handled.
Edit2: I’m a software engineer (and, as of recently, small-scale farmer) originally from the US and living in Japan for nearly a decade now.
So the biggest problem, particularly with the currency and economy, is that Japan lacks a lot of resources so a ton of things are imported. This means that a ton of things used by normal people are going up in price, especially since corona opened the floodgates on that (Japanese makers were really resistant to changing prices but corona gave an excuse and momentum came in). For most Japanese, that’s just going to impact goods and services. For most foreigners, they want to go home to see their family sometimes and their wages mean much less and flight prices get higher. Overseas vacations in general are an issue here. If there’s an emergency, it’s even worse.
Two types of long-release ADHD medication are currently allowed for adult ADHD in Japan. Instant release and other varieties are very illegal. Concerta was the only option until fairly recently, but now another one is allowed (though English documentation is probably behind).