Background

Looks to me like he was never in Japan, Whenever you see the Bogey character on location its always from behind or obscuring his face.

It's called rear screen projection. They are actually on a studio set and the background is a screen that they project an image on.

As the other poster mentioned Bogie never went to Japan they just used a double in the street scenes and for any shots of Bogie's face they used the rear projection.

It was used a lot in older movies. Sometimes it's obvious, sometimes it's not as noticeable. As film techniques improved they used the process less and less because it became too obvious and other methods became available.