SHINSHIRO, Japan — Toshie Yamada’s “kei,” with its pint-size engine and tiny wheels, looks more like a Fisher-Price toy car than a regular truck. But don’t underestimate her Nissan NT 100 Clipper microtruck. At a recent farmers’ market, where she sells orchids from her flower farm here in central Japan, she loaded up a mountain of crates, buckets and a folding table before hopping in and zipping away.

“In these parts, keis are definitely the No. 1 car,” Ms. Yamada said. “Big cars are too much of a hassle.”

As farmers’ trucks, family cars, delivery vans and even tiny cafes-on-wheels, keis are everywhere in Japan. They are more popular than ever, thanks to the country’s high gasoline prices, a preferential tax system and an uneven economic recovery that have made the wee cars enticing value propositions.

Keis have terrific fuel economies that rival the Prius, but they sell for half the price. Last year, a record 40 percent of all new cars sold in Japan were keis.