I'm aware that foreigners are required to have their passport with them at all times in Japan and that the police may stop you at any time and ask to see it.

Today, for the first time in ~20 visits, I was stopped and asked for my passport, which I always have with me when in Japan. Not having had this happen before, I'd like to ask those more experienced if my particular instance was legitimate.

This happened today (Sunday) at 4:00 PM at Kawasaki Station, at the top of the escalator leading to the JR gate level from the East entrance/exit. As I got off the escalator and headed for the gate, a Japanese guy not in police uniform approached me and said something. Since my Japanese language skills are pretty much non-existent I kept moving, thinking it may have been someone soliciting for a charity. He then showed a badge that said "Police" and was joined by another guy, also not in uniform, who showed a similar badge. I don't recall details of the badges other than that they said "Police", looked to be made of brass, and were in leather cases.

I was asked for my passport, which I handed to the first guy who had approached me, and he started to look through it and write down some details in a notebook while the second guy tried to converse with me in Japanese - and in turn I could only say, in English, that I speak English only.

I was not touched, I was not searched (I had no bags with me, no backpack, no jacket), I did not feel as though I was being hassled, and I did not feel that they were going to run off with my passport - i.e. it seemed reasonably legitimate to someone who hadn't been through this experience before.

The one thing that gave me pause was that they didn't seem super proficient at writing down my passport info, especially since they took down my first and middle names but not my last. I would expect that police who do this on a regular basis would seem more familiar with a US passport. Other than record the passport details and look at the most recent landing stamp, nothing else was done and I was sent on my way with a "thank you".

Was this a legitimate police stop? Japan is one of the last places I'd expect to find fake cops but that doesn't mean there aren't any.