If proof were ever needed of just how industrious the Japanese are, a quick trip to a city park on a sunny afternoon should be all that’s required. This last weekend in Tokyo was typical of the early summer. Hot but not too hot, still a few notches below the raging humidity of the rainy season and the fierce heat of high summer. Ideal weather, you might think, for lounging in the park.

Yoyogi Park is one of central Tokyo’s largest open spaces, a green lung in a densely built-up area. It should be the perfect spot for a quiet afternoon of doing nothing. Except that nobody is. As soon as you walk into the park from the west side, you are nearly flattened by a stampede of impossibly fit runners. Having crossed the running lane, you come to a cycle path where children are racing on small bicycles alongside twosomes on hired tandems. Gardeners wearing headscarves and split-toed shoes stand on ladders clipping pine trees.

The area of open grass in the middle of the park is filled with more activities than the average community centre. Under one tree a group of women is taking a class in Hawaiian dance, swaying their hips unselfconsciously as their music wafts around the park for everyone to hear. Nearby, a photographer and his team are in the middle of a shoot, snapping three relentlessly cheerful children in day-glo fashions.

A lone saxophonist, clearly not wanting to bother his neighbours at home, is practising his scales. He’s out of synch with the drummers who are playing their own music nearby. And in the shade of a tree, a large plastic sheet has been laid out for an office picnic. Indoor house rituals are adhered to as everyone carefully removes their shoes and leaves them at the edge before stepping on the mat.

One deeply tanned man is a park regular. He is there almost every weekend entertaining crowds of children with buckets of soapy liquid and homemade contraptions that unleash torrents of bubbles. Why he does it is something of a mystery. He doesn’t ask for money and doesn’t talk to the children but they chase him and his bubbles all over the park.

Even the dogs are busy in Yoyogi where they have been allocated three separate runs for large, small and very small dogs. A trio of freshly shampooed Yorkies seem to be reveling in their brief moment of liberty, delighted to have been released from their prams.

In the midst of this mayhem is an outdoor yoga class. Quite how they’re finding their centre in this less than tranquil scene is hard to imagine.

What few people are doing is nothing at all. One woman – not Japanese – is bravely sunbathing in a bikini. It’s not the done thing, even on the hottest days and nobody else seems interested in doing anything so idle as working on their tan anyway. They are too busy flying kites, throwing Frisbees and playing badminton. A homeless man snoozes, oblivious to the picture of productivity before him. But otherwise everybody is doing something.

It’s as if free time spent doing nothing is wasted. In a city where most people live in shoebox-size apartments, the park becomes a sports venue, community hall and theatre rolled into one. For those of us who aren’t brushing up on our juggling skills or perfecting one of the lesser known martial arts, it also provides an entertaining afternoon of a far less strenuous exercise: people watching.