The new Daihatsu Vision Copen concept hints at the roadster breaking from its kei car roots and becoming a full-sized Mazda MX-5 rival.

Japan's kei rules bind cars to being no more than 3400m long and 1480mm wide and having an engine no larger than 660cc.

Yet the Vision Copen measures in at 3835mm long and 1695mm wide – slightly shorter and narrower than the current MX-5 – and packs a 1.3-litre powerplant.

Bar styling that apes the original Copen, the new model is an entirely different proposition, switching from front-wheel drive to rear-wheel drive.

Daihatsu is yet to provide detailed specifications for the new Copen’s engine, beyond its displacement, which is almost double the 660cc of the current Copen’s 63bhp turbocharged triple.

Nonetheless, the Japanese brand did confirm that the new engine is capable of running on carbon-neutral fuels, such as e-fuels.

Toyota, which took full control of Daihatsu in 2016, confirmed in June that it was working with “various partners” to trial e-fuels. It's exploring their use as a means of reducing the net carbon emissions from cars already on the road and in regions where neither hydrogen nor battery electrification is viable. 

E-fuels are claimed to be carbon-neutral because they're synthesised using carbon from the atmosphere, sourced by carbon-capture systems or by using waste biomass.

This initial removal of CO2 for their production is argued to offset that which they emit when combusted.

The Copen's new front-engined, rear-driven configuration has been designed to offer “the ultimate in driving joy”, said Daihatsu.

The car also appears to use an automatic gearbox, in keeping with Japanese market trends.

The Vision Copen is expected to translate into a new, third-generation Copen by the middle of the decade, the current car having been on sale in Japan since mid-2014.

It isn't expected to go on sale in the UK, given that Daihatsu left every European market in January 2013.

Daihatsu also unveiled three battery-electric kei car concepts at the Tokyo motor show: a customisable city car, a high-riding convertible and a delivery van.

The city car, dubbed the me:Mo, is designed around the prospect of long-term ownership. Its interior and exterior can be modified according to “changes in the customer’s stage of life”. For example, the front-passenger seat can be swapped out for a portable sandpit and the centre console can function as a large bin for toys.

The convertible, the Ospano, is a similar concept with chunky plastic bumpers and a simple interior design. It's slightly shorter than the Smart Forfour and is said to offer “relaxed enjoyment” through a driving experience comparable with “taking a walk”.

The delivery van, dubbed the Uniform, is said to be highly adaptable. It's available with a variety of exterior parts to suit different businesses, as well as a power-take-off socket to supply electricity to external devices.