According to Kotaku the Japanese actor (and general celebrity) inserted into these Into Darkness scenes is Shigeru Izumiya. They also provided the following pithy explanation of events in the advert:
Scotty says the ship is going to rust, but Izumiya says the 5-56 spray will prevent that from happening.Into Darkness only opening in Japan last month, hence this latest promotional partnership only coming about now. But there have been plenty of other weird and wonderful tie-ins, check out the promotion section on my Into Darkness guide page to have a look at some of the other adverts associated with the film.
Then, Captain Kirk asks Spock if he's an acquaintance, and Mister Spock says he doesn't know the guy. (I don't blame him!)
The next shot shows Japanese Spock telling the Captain to sit down.