It is a tribute, with at least some degree of creativity and effort put into making the video. I don't see this being exploited to gain Google any more users than, let's be honest, they would have anyway. Especially since it is on Google Japan, I would anticipate people going to the main page, watching the video, and then not even performing a search. And in instances where that does occur, Google is gaining nothing financially from something which, again, is a creative tribute.
I don't really see it as shilling at all.