It may not be a car, but Honda's U3-X was one of the most impressive concepts at the show. Designed in Honda's advanced design studio in the Roppongi district of central Tokyo, the U3-X is an electric unicycle that employs the gyroscopic system from Honda's Asimo humanoid. Though Asimo was not present, the U3-X was presented in various trims, including an attractive graffiti theme, while the EV-N concept showed how it could be stowed in the door lining of a car.

About the size of an upright skateboard, the U3-X's 'number 8' styling houses seat pads and a ring battery in the upper part, while the lower circle contains the wheel, motor and gyroscope. But it is the wheel that deserves mention here, for without it the U3-X could not be: in place of a single wheel that rotates about the vertical axis to steer, the 'tire' of the U3-X is made of many smaller casters strung like beads on a necklace, each separately powered. That means the device glides left or right according to body gesture, rather than rotating. But more surreal still is the self-righting gyroscope, meaning that it remains upright even when dismounted.

The technology on its own would impress, but what makes the U3-X so satisfying is how well wrought the styling is, and how directly it relates to the incredible package. The double 'O' motif is simple and clear, dividing the object into machine and user, and the manner in which the seats fold out recalls the Butterfly stool of Sori Yanagi. It is honest, and despite the advanced technology feels friendly and well-suited to the domestic context Honda foresees. It is also notable for being part of a new wave of electric self-mobility products (best expressed by the Segway and Toyota iReal) that point to a significant future market owing to downsizing and the propagation of pedestrianized streets. Honda is said to now be looking into feasibility for production, though to leave the U3-X as a research program appears too big an opportunity to miss.

The Tokyo show wouldn't normally be pertinent to the Infiniti brand - as it doesn't sell in Japan - but the new Nissan Fuga did inadvertently become the first full-car preview of the next Infiniti M due next year, as it is a straight re-badge of its upmarket sister model. Though the Infiniti M was previewed at an exclusive event in Pebble Beach in the summer of 2009, it showed no more than a model and a 3D presentation.

Consequently, the Fuga is significant on a number of levels and becomes possibly the plushest production Nissan ever made. The four-door sedan's exterior is akin to a BMW 5-Series in size - with near identical width - but a significant 96mm longer and 32mm taller. Visual interest to differentiate its three-box shape comes in the form of pleasingly pronounced front wheelarches that flank a curving sunken hood - just as on the Infiniti FX50 SUV. A wavy feature line, starting from the back of the front headlamps, runs parallel to this front wheelarch-echoing line before experiencing a pronounced under pinch below the wing mirror and then curves gently downwards through both door handle scoops before kicking up and round again at the rear wheelarch.

The interior is arguably even better. The IP wraps around into the doors on each side from a center console featuring a waterfall-style step section that merges into a high transmission tunnel. The dashboard and console utilize extensive high quality curved real wood veneers that fade from dark to light from the edges inwards - a treatment design boss Nakamura says comes from traditional Japanese Maki-e techniques using shiny lacquer tinted with silver powder. Elsewhere, an analogue clock, overt stitching around the driver dials binnacle and waxy soft-touch leatherette covering the center armrest help to engender a strong luxury feeling. All are clearly upmarket details designed for the Infiniti brand, but meanwhile Nissan's Japanese customers have never had it so good.

This is a significant concept, if not for its visual design then for its packaging and technological achievements. It is a 3.1m long Kei car that seats four adults, contains all of the safety and entertainment features you would expect and weighs in at just 700kg by the use of lightweight high tensile steels, plastics and a rethink of its interior components. The engine is an evolution of the current 3-cylinder 660cc KF powerplant with the ECO Idle stop start system. This achieves over 30km/liter (72 mpg) fuel economy and greatly reduced CO2 and will find its way into future Daihatsu products. In a world where cars have been increasing in weight for the past four decades this is a welcome and timely rethink.

As a concept demonstrating this forward thinking technology however it is a shame that the design of the vehicle is so comprehensively unadventurous. A blunt proportion, conservative surfacing and use of inexpensive production oriented light details lend this concept a dated production car image. Although generally well resolved the side surfaces and graphics tread a well worn path with a simple shoulder line and negative highlight catcher in the door lower. The rear of the vehicle uses a one-piece transparent hatch which reduces components, but which utilizes external hinging doing little to create a fresh image.

The interior fares little better with no originality in the architecture or unique visual language, the most interesting piece of design being the seating, which combines an intelligent use of netting and lightweight steel to massively reduce weight over a conventional system.  All in all a step forward for weight reduction technology and recyclable manufacturing, but a bolder and more courageous design direction would be welcome.