Most of the Japanese who were interred were farmers from California. At the time there were not many Blacks in CA. Most of their goods and lands were purchased cheaply by their neighboring farmers-- mostly of "White" origin or Italian immigrants.
My father bought a horse from a Japanese who was forced to sell everything. It being WWII, he called the horse "jap".
You may find some examples of Blacks buying Japanese property, but it certainly wasn't a common event.
When the Japanese were freed, they simply had to start over with what cash they managed to retain after selling all their belongings.
