Looking like a white Batmobile Junior, the hybrid concept combines the long roofline of the Prius with the compact dimensions of Toyota's Yaris light car.
Despite its similar dimensions, the FT-Bh concept weighs in at just 786kg, making the circa-1030kg Yaris seem positively portly by comparison.
Driving the hybrid concept is a two-cylinder 1.0 litre petrol engine, paired with an electric motor - a combination that weighs more than the three-cylinder 1.0 litre engine available with the Yaris in overseas markets.
Because of that extra bulk in the powertrain, Toyota reduced the mass of the bodyshell, interior trim, chassis and electronics by around 340kg to achieve its target weight.
With its ultra-light body and efficient hybrid system, the FT-Bh lists fuel consumption figures of just 2.1 l/100km, and carbon emissions as low as 49g/km.
By comparison, the overseas Yaris Hybrid, which pairs a 1.5 litre petrol engine with an electric motor for an overall 74kW, returns 3.5 l/100km - appealing enough figures on their own.
Part of the concept's excellent fuel economy comes from its aerodynamics: a co-efficient of drag of just 0.235 compares with 0.25 for the Prius, and an average of about 0.29 for a B-segment car.
The FT-Bh has been designed to keep manufacturing costs down, using materials already becoming common in the industry, and all with a focus on introducing the new model at a competitive point in Europe's hard-fought city-car market.
"One year ago we challenged our engineers and designers to come up with a small super-efficient car at an affordable price, reinforcing our environmental leadership in the coming years," Toyota Europe boss Didier Leroy said.
"The FT-Bh combines full hybrid efficiency, advanced aerodynamics and ultra-lightness - all achieved at a cost-level appropriate for a high-volume B-segment (light) car."
Will we see the FT-Bh on the market in the future? Not in its quirky concept guise, but with a name that stands for "Future Toyota B-segment Hybrid," it's likely that we're looking at a technical preview of what Toyota has in store for the future.
As for its bizarre styling, Toyota says the FT-Bh was designed around a new "Ecomotion" idea, with key panels formed to represent the way fabric can be stretched taut between fastening points, to reflect their ultra-light weight.