Japanese auto makers aim to captivate drivers with environment-friendly concept cars at the Tokyo Motor Show, showcasing technology they hope will set a global standard for a rapidly growing segment. Toyota Motor Corp and Honda Motor Co Ltd, Japan's top two, set a world first last year when they put on sale fuel cell vehicles (FCVs), which run on hydrogen and emit only water as a by-product. They are also alone in selling fuel-efficient gasoline-electric hybrid cars by the tens of thousands.