If you were from an American concept company, it would be difficult to adjust to a Jap company. The culture is totally different.
If you miss the old lifestyle and environment your previous co had to offer, maybe you can think about it.
And if you left on good terms with your boss and management, you can consider contacting your boss and see if there are any other vacancies around in other depts or the same dept.
Otherwise, there is always an option of looking for a new prospect in another company, maybe a competitor with the same culture you used to work in? That would be a new challenge and change.
Good luck!
