Japan had sixteen POW camps for their 4700 POWs, and prisoners were for the most part humanely treated. Japan at the time was trying to gain international recognition as a civilized nation, so they made a very concerted effort to follow the Hague convention for the humane treatment of prisoners.

POWs weren't put into forced labor but paid a wage based on rank, with the money intended towards improving their own situation by buying clothing and whatnot. They were further allowed to leave the camp and engaged in skilled labor for additional wages.

There was an additional provision we don't see much today where they were allowed to go on parole by signing an agreement not to join any of the German armed forces.

The Bando POW camp in Tokushima in particular gained a small amount of fame as being the first place Beethoven's 9th was performed in Japan, and would grow to be very popular afterward.

After the war some former POWs chose to remain in Japan, continuing on in the jobs they'd engaged in while prisoners. Considering the state of Germany post-war it's believable.