In linking to The Los Angeles Business Journal's article on Japanese businesses in Torrance, Mark Lacter's LAOBSERVED business blog states there is no obvious reason why this is so:
Japanese in Torrance: The city is home to at least 246 companies that are either units of Japanese companies or founded by people of Japanese origin. That's at least 44 more than the city of L.A. There isn't any obvious explanation for the Torrance contingent, other than it's a relatively business-friendly community and very close to the port and other major transportation networks.
Actually... there is a very obvious reason!
Just look at a map. Almost directly east of Torrance is Gardena which for most of the 20th Century had a very large Japanese population due to Japanese-American run truck farms that started not long after the turn of the last century. Even the latest census shows an almost 30% Asian population in Gardena. Then when that community prospered, the nearest middle/upper middle class community was Torrance and they started moving west setting up stores, restaurants, supermarkets, language schools, churches and temples - proving the social infrastructure for the incoming Japanese companies.
And with Torrance having the necessary land for the new offices and factories (and a glut of cheap space after the aero-space industry collapse) and a superb school system, it had advantages that none of the other Japanese-American communities in LA County had.
Therefore - it became the headquarters city for major Japanese companies.