The cast - 3. The game designer

In the beginning there was Word, and Word and Excel. As a game designer in Japan your job title would be “planner" and your toolbox would be Microsoft Office, more likely than not the Japanese version. Powerpoint and/or Word for initial design and pitch-documents and after that Excel for everything else. Bear in mind that I’m generalising here.

Don't expect to be the God of the game design, though. You will answer directly to the producer and, if he feels like a managerial decision is called for, the boss. In fact, you may have certain things dictated to you, and you'll just write them down in Excel sheets. If you're working on, say, a racing game or RPG be prepared to write page after page of specs, test them out, rewrite them, etc.

Other tasks often include asset control; creating naming conventions and asset lists, running between programmers and artists constantly adapting the list and annoying everyone by making them redo and re-export stuff as slight changes are called for. Even, if the task hasn't been assigned to the leads, as it should be, you may find yourself writing schedules.
Of course you will also be working on level designs, but as mentioned above you will play second fiddle to the producer but it will be you who does most of the hard work.

Because of the software and the lists you need to create for the rest of the team your Japanese should be pretty advanced, with very competent reading and writing abilities. You'll also need to discuss and check with other team members as they do their work and follow your designs, so good speaking skills are also a must. You will also be in meeting after meeting getting game designs dictated to you by your superiors, followed by meetings where you dictate those designs to the rest of the team.

There doesn't seem to be the same kind of career structure for planners as in the west; as there are no real QA departments to promote aspiring designers from. I'm not sure where these planners come from or what background they usually have, but it isn't in code or art. As such the naming conventions and asset lists are usually very rough and full of mistakes and oversights and require constant reworking. If you want to actually be the auteur you’ll have to work your way up to producer. But being a planner isn't necessarily the career path to producerdom. These seem to spring up from all disciplines, from art to code, and are often chosen for longevity and not necessarily skill.

What with the high levels of Japanese required, as well as the many obscure differences in tastes becoming a planner in Japan may be one of the more difficult careers for the aspiring foreigner. Indeed, I have not met any yet. I wouldn't say it's impossible but be prepared for a lot of hard, underpaid work and many dead-ends.