The nation's automakers have long relied on parts from domestic sources that are part of their "keiretsu" corporate groupings, but now they are turning to imports to cut costs and survive growing global competition.
South Korean producers are increasingly being sourced for the parts, as their prices are lower than their Japanese counterparts and of better quality than parts made in China, analysts say.
"It is possible the number of South Korean-made parts introduced by Japanese carmakers will double in about five years," said Hitoshi Kaise, senior project manager in charge of the auto industry for consulting firm Roland Berger Ltd.