I worked in Japan for 3 years as a technical translator and the better part of 3 years as a software engineer at a large software consultancy. Software engineers do lots of things, but theoretically the main reason I was there was to develop software (mostly Big Freaking Enterprise Java web applications, for universities, and software which supported the development of the same).

I would be happy to talk to you about that experience at length. The capsule summary is that I cannot recommend working for a Japanese megacorp as a means of broadening one's horizons unless one has the very specific desire to learn about Japanese megacorps. The work/life balance works out such that -- even if you enjoy software development very, very much -- you will likely have insufficient time/energy/health to see much of Japan in your rather few non-working hours.