Encounter with the Law Enforcement

My bicycle in Amsterdam
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A couple months ago, in a train station, I was stopped by a policeman. Of course I had no idea what he is talking about, later my friend caught up with me and translated the policeman's request. "Um, miss, there are a lot of people in this station today, beware of pickpockets" Seeing me with no response, he turned to my friend and asked him if I am a foreigner. After the confirmation, he asked me "Do you have the foreigner registration card?" Of course, I have got it in my wallet. This was actually a bit disturbing to my friend, because the policeman just singled me out from hundreds of other passengers, asking for my I.D.. I don't particularly looked foreign but...

I came back to Tokyo and joined the Sunday rollerblading. As we came to our first stop near Tokyo station, I saw a couple of friends who I haven't met for almost half a year. Excited, we were screaming and pushing around a bit, then the security guard came to me and asked me to take off my rollerblades. I was like, um, "Is it just me? Why not others?" The guard showed a distasteful face and replied me in English "All". Fine, I duly took my blades off, and the guard disappeared (I guess he figured he cannot get the whole group to obey his order, better walked away before losing more face). Well, there were 30 other skaters around, he picked me to show his authority.