TL;DR: More than just (but also plenty of) giant monster battling
Big Man Japan (大日本人) is a film directed by and starring Hitoshi Matsumoto (松本 人志) who many people might know as part of the comedy duo Downtown along with Masatoshi Hamada (浜田 雅功). Downtown are the guys that every year organise and participate in 'zettai ni waratte ha ikenai' (絶対に笑ってはいけない）which is a highly entertaining and sometimes troubling New Years special which every year the majority of my Japanese friends watch. It deserves it's own post so I won't go into it too much except to say that 'Big Man Japan' has a vastly different style of humor than what you might expect if you are a fan of Downtown.
One of the things that I like about the Japanese entertainment and film industry is that somehow (I'm not sure if it's due to the way audiences react or something within the industry itself) it is more acceptable for entertainers to cross over and do a variety of things. Whilst Matsumoto is seen mainly as one of Japan's most popular comedians and show hosts he is also respected as a writer/ Director of films which have quirky story lines that aren't based soley on humour but provide interesting social commentary as well.
I started watching Big Man Japan thinking that, as a film about a man who can grow giant in order to battle weird giant monsters Godzilla style, it was gong to be full of slapstick Downtown style humour. However whilst there was some of that in places there was also a lot of more restrained and very dry humour going throughout the film, particularly in the mock vox pops which can be seen in the trailer below and in the plight of Daisatô, the 'Big Man Japan' as he struggles to save the Japanese public that have lost interest in him.
Pretty early on in the film it becomes very clear that Daisato is being used as a metaphor for modern Japan and once you see that comparison everything else in the film fits into place as an compelling yet slow paced social commentary. Although I did find the film a little slow in the middle, I think this was partly due to my misconceptions of what kind of film it would be and partly because the CGI is a little cringe worthy. I understand that the film wasn't made on the same kind of budget as a hollywood film however I think that the monster fights might have been achieved in a different, possibly more creative way. I would have loved to see some more of the power ranger/ Ultraman-esc costumes that can be seen at the end.
To be honest though the ending really made up for all of that. It remains one of my favourite moments in Japanese cinema and keeps in line with the bleak social commentary on modern Japan and how it interacts with the international community as well as just being extremely random and off beat.
I do think that much of the film's humour and subject matter is quite uniquely Japanese and might be difficult to get across in translation however the ending scene at the very least was something I was able to show my brother (who speaks no Japanese and has never been to Japan) and have him really appreciate (he was in stitches). Matsumoto himself said in a radio interview that he never intended this film for international audiences and it is easy to see that. This is why when I heard that there were plans for Columbia Pictures to do an American Remake I was baffled, and then nauseous and then baffled again. If it ever does get made I know that it's going to go the way of the US version of Kath and Kim.
All in all, I have a lot of love for this film and would highly recommend it, though the humour may not be what you would expect given the story line and the social commentary hard for non-Japanese audiences to follow.