Matteo Renzi of Italy and Canadian leader Justin Trudeau were bundled into eco-friendly sedans for an achingly slow ride around a carpark that ended with the photogenic pair dropped off for the talks, which are being held southwest of Tokyo.
European Commission President Jean-Claude Juncker and European Council President Donald Tusk also got a very uneventful crash course on the cars, which are powered by hydrogen and emit only water from their exhaust pipe.
Japan is a world leader in the technology which is seen as the Holy Grail for an industry increasingly shifting focus to green solutions, including electric vehicles.
US president Barack Obama and Germany's Angela Merkel were among the other Group of Seven leaders noticeably absent from the ride along, which was overseen by Japan's premier Shinzo Abe.
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Earlier, Nissan was giving the world's press a look at vehicles that park themselves - indispensable for drivers who break into a cold sweat at the thought of parallel parking.
Honda looked to win hearts with its experimental take on hands-free mobility - the cute-as-a-button Uni Cub B. The stool-sized contraption glides in line with users' movements, a kind of seated-Segue with an R2-D2 charm.
"We wanted to demonstrate Japanese technology to the world," said Reiko Katsumura, a department manager in Honda's mobility business, who worked on the project.
Katsumura, however, admitted there was another motive for showing off the little creation to the world's press - finding a decent use for it.
"But it's the same as having a camera in a mobile phone. People used to ask why have a camera in a phone. Now it's everywhere.