You can look up unknown callers by number on:
If it is a company or institution, the owner of the number is listed. if it is a scam number there’s usually a string of Japanese comments about the nature of the call and curses directed towards the caller.
I look up every call on this site.
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The advantage of using this over Google Maps, for example, is that gives statistics about how many enquiries have been about this number and human curated evaluation of the number. Also, numbers that are not businesses are listed and black businesses and numbers used to make sales calls are listed which won’t necessarily be listed publicly.
If you put the number into Google, jpnumber.com will often be the first suggestion. Just click through to jpnumber and see what people are saying about it.
by stuartcw