Many Japanese corporations such as Nissan and Toyota invested heavily in the UK while Britain was still a member of the EU. Exporting into the EU often meant heavy tariffs(roughly 15% on automobiles), many firms, Japanese and otherwise invested in British manufacturing facilities to sell into UK market and export to Europe rather export from outside the EU.
With Britain leaving the EU many international business interests will be watching these trade negotiations to see how UK and European trade will develop in the post-brexit landscape.