They are under Nissan, however they are classed as an American company as their first cars were sold in USA and hardly any Infiniti's are actually sold in Japan. So really it is a American car company owned by Japan. if you want to read up about it here is a Reddit discussion about a similar thing in GT7: https://www.reddit.com/r/granturismo/comments/9gpvhw/why_is_infinti_in_the_american_dealership/