‘Tis the week for tiny Japanese sports cars. Yesterday we saw the Honda Small Sports Car EV– a dinky all-electric concept – and today Daihatsu has released a few sketchy details and pictures of its D-X concept, a two-seater roadster set to be unveiled at the Tokyo show later this month. Unlike the Honda, the little Daihatsu isn’t electrically motivated, but has an equally interesting powertrain: a new two-cylinder turbo petrol engine with direct injection. Daihatsu hasn’t revealed how big that engine is, or how much power it’ll produce, but it’s safe to assume it’ll be (a) little and (b) not very powerful. Daihatsu claims the D-X strikes ‘a balance between the joy of driving and fuel efficiency’, and kei-car regulations suggest its two cylinder engine will displace around 660cc and produce 60-something horsepower. The current Top Gear two-cylinder of choice, Fiat’s lovely little ‘TwinAir’, displaces 875cc and makes 84bhp in turbocharged guise.We’re told the D-X uses a ‘resin-based body’ – some sort of plastic composite, in other words – with removable panels. Shorn of that strange black plastic cladding around the sills and arches, the Daihatsu might actually look quite normal. In fact, can anyone else spot a Jaguar-aping front end hiding under there.Daihatsu isn’t revealing any more about the D-X, not least whether it’ll be considered for production. If so, it could replace the similarly kei-car-based Copen, which has been built since 1999 and is surely creaking towards retirement.As part of its ‘Big Answer from Small’ philosophy (a slogan we can only imagine made more sense in Japanse), Daihatsu will also use the Tokyo Show to unveil a couple more bonkers concepts: an all-electric Renault Twizy-style scooter-car, and a bizarre two-seat pod powered by a fuel cell.But we’re most interested in the midget D-X. Are we witnessing the dawn of a new generation of mini-roadsters? Will we soon herald the Smart Roadster as a car far ahead of its time? Or are we, as usual, desperately hunting for a trend that doesn’t exist?