The three big factors involved are lower personnel costs, lower auto parts costs and increased productivity because of newer, more efficient factories. Companies can save ten percent on personnel in Kyushu versus traditional manufacturing centers like Aichi and Kanagawa, which are on the main island of Honshu and near major cities like Nagoya and Tokyo. Kyushu is also much closer to the South Korean peninsula, and the weakness of the South Korean won means importing lower-priced Korean auto parts is an even more attractive option.
Japanese newspaper The Asahi Shimbun says it could soon be the Detroit of Japan. The prediction could be sped up if intergovernment talks can rework laws on transportation: it's illegal for trucks with South Korean plates to drive on Japanese roads, so trucks hauling parts get shipped to Kyushu ports and their cargo is transferred to Japanese trucks. Japanese and South Korean officials are working to determine how to allow trucks from across the strait to travel unhindered from Korean auto parts factories to Japanese car factories.