Petri Artturi Asikainen would regularly accost strangers in Tokyo, on the streets, in parks or bars and on trains. With a high-end Nikon D3 digital SLR in his hands, the lanky and bespectacled Finn would ask — somewhat timidly summoning one of the few Japanese phrases he had memorized: "Can I take a picture of you?" If the answer was in the affirmative, he'd then fire off another, even more personal inquiry: "How old are you?"

On and off, the freelance photographer kept on making such rather sudden contact with Tokyoites, day and night, for about three years. In all, he reckons he approached around 2,500 people — and succeeded in taking pictures of nearly 500 of them.

Finally, in 2012, he put together a series of 202 portraits — presented as 101 man-and-woman pairs — of people in the city aged right the way through from newborns to centenarians. And, in December last year, the fruits of his three-year project revealing an amazing diversity of life in this city of some 13 million people finally became available in a photobook titled "100 Years in Tokyo."