They aren't from my experience working in two major Japanese companies. Sometimes they'll pay your network bill if WFH is allowed, but that's basically it. Not sure about smaller companies, but honestly, I'd be surprised.
e.g. https://www.gtalent.jp/blog/japanwork-en/social-insurance-we... or https://www.reddit.com/r/japanlife/comments/54fjgf/how_much_...
I know 3 Japanese people (nothing to do with foreigners or foreign companies) that had their house paid by the company totally or partially, and they told me it was common in their company/industry. And those were large industries (train company, hospital, manufacturing).
Mine is anecdotal, but from how they described it it's an anecdote involving hundreds to thousands of people indirectly, so I'm very confident that it's not an isolated thing.