Mention street art in Tokyo, and anyone familiar with the city will wonder what you're talking about. Sharp eyed observers might have spotted a few pieces of graffiti around the biggest stations and under railway bridges in the suburbs, but for the most part, the walls of the city are untouched by freelance street artists.

Nor are there many murals, the officially sanctioned street art that adorns the walls of apartment blocks, bars and fashion boutiques in big cities like New York, Melbourne and London. Shibuya station has Taro Okamoto's Myth of Tomorrow, but nothing to rival Mexico City, the city it was originally created for, where the mural has become a form of national storytelling.

Graffiti has always existed in western cities, but it only became artistic in the '70s. It was all about bombastic self-aggrandisement and thrived in neglected neighbourhoods, where young people were hungry to make their mark.

Since the '80s, graffiti has morphed into street art and become part of a challenge to mainstream art, being untrammelled by distinctions between high and low art. Street art is attention-grabbing, didactic and often has a political dimension, which explains its popularity in polarised cities like Bogota, Rio de Janeiro and Gaza.

But expand your definition of street art a little and you'll find that Tokyo is rich in public self-expression. There's not much in the way of graffiti, but many artists write on stickers, which they then post on walls, doors and air conditioning units around nightlife hubs like Shinjuku, Shibuya and Harajuku. Others use stencils, or printed blow ups of their work.

Some shop owners are happy to have an artist enliven their shop front with a work of art. Many Japanese artists take their cue from manga, like this clothes shop in Harajuku....

...while others are inspired by the monsters of Japanese folklore, like the creator of this mural in Okubo.

Some street art is designed to provoke, like these hand grenades on the side of a vending machine in Ueno...

Some is designed to reassure...

...while other works are more ambivalent.

A lot of the art you see on the street functions as advertising, like this mural for a pipe company in Okachimachi.

This shopfront in Asakusa is also advertising something, though it's hard to say what it might be.

Other times, it's enough to just give window space to an artist, like this window in Shinjuku...

And sometimes street art is nothing more radical than decorating your front window with animal figures paying homage to their favourite jockeys, like this creation in Kuramae.

The point is that the streets of Tokyo abound in artistic expression. Most of it is a long way from what is usually understood as 'street art,' but it adds up to a feast for the eyeballs of a kind you can only find in the Japanese capital.