When Honda Motor Co. launched the latest version of its N-Box a year ago, it promoted features on the pint-sized minicar such as error-detecting pedals, automatic emergency braking and moveable seats, part of a push to market the vehicle to young families. But a drastically different demographic has made the N-Box the country's best-selling passenger vehicle: roughly half the owners of the most recent model are 50 or older. Automakers had hoped high-tech options would attract younger buyers to kei cars (minicars) even as the number of Japanese drivers under 30 has slid nearly 40 percent since 2001. Instead, with a price tag starting around ¥850,000 and low ownership taxes, minicars have gained a more loyal following among the rapidly growing population of elderly Japanese, many of whom are on fixed incomes. "After their children are grown and leave home, more people are looking to downsize from larger family cars to more compact ones," said Kiminori Murano, managing director at Tortoise, a dealership specializing in minicars in Yamato, Kanagawa Prefecture.