If you're an outgoing person, this might be something to look at. Japanese companies are always looking for good sales people, and since the typical North American salesperson has difficulty relating to Japanese culture, your background could be a big plus. Human Resources I think this is the biggest overlooked opportunity for those with Japan Experience. Leaving the Japan connection aside, HR is a great field for those with liberal arts backgrounds, because it requires good interpersonal and communications skills. And in Japanese companies, your knowledge of the culture can be extremely valuable in helping to smooth over intercultural conflicts.
Some firms are willing to hire people who have no prior experience for human resource positions.
In some larger organizations you may also need a Master's degree in order to really progress in this field. If you don't have a clear idea what type of job you want to get eventually, you won' t get as much out of it as you could. Or you could find yourself funneled by inertia into a consulting or finance job where you work 80 hours a week or more. Finally, although b-schools such as my alma mater U. Chicago are making a concerted effort to become more international, going straight from the Japan Experience into business school is like jumping into ice cold water. I remember recruiters looking at my r sum like I had gone to Mars instead of Japan, and being frustrated with some of my very provincial classmates.