Folks in Tokyo are not especially well-known for open friendliness toward strangers---especially when the stranger is non-Japanese.
However, sometimes when I am out with a camera, people who would normally never approach me will suddenly become very talkative. Usually they are older people, but occasionally even the munchkins can't resist:
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"What are you doing?" he asked as he rushed over to the spot where I was taking photos.
"Taking pictures," I replied.
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He watched me for a few seconds before running over to stare at the scene, apparently wondering what was so special about the bike that I'd be photographing it.