The statistical evidence backs this up: pure electric vehicle sales in Japan are a tiny fraction of total vehicle sales -- less than 1% -- and sales are not growing significantly.
The headline is linkbaity and meant to play on people's unfounded stereotypes of Japan as some sort of environmentally superior Utopian Tomorrowland.
Only about 30,000 plug-in vehicles are sold per year in Japan[1], out of 4.2 million total passenger vehicles sold.[2]
Growth forecasts for plugins are anemic, with even the most optimistic estimates predicting only 50,000 units sold annually by 2023.[3]
I think Japan is at least better than the US environmentally in a number of ways, but a lot of the benefit is squandered away by things like overuse of air conditioning, packaging waste, and industry.