The Japanese Americans who were interned in WWII were not all released at the same time. There were various stages along the way.
Early on, for example, internees could be released if they could show they had a job waiting for them and if someone on the outside would vouch for their loyalty. Around 15,000 internees were released in this way in 1943. This number increased as the war went on.
There were also those who were released to go fight in the war. In 1943, Japanese born in the US were made eligible to join the Army and go to Europe. Many chose to do this.
The camps themselves were ordered to be closed in 1945. By the end of 1945, essentially all of the Japanese Americans who had been interned had been released.