What is the theme in Journey to Topaz by Yoshiko Uchida?

Freedom is a major theme in this book. Yuki and her family are living in the United States. She and her brother Ken are citizens of the United States. Mr. and Mrs. Sakane are prohibited by law from becoming citizens, even though they have lived half of their lives in the United States and are productive members of society. Like hundreds of thousands of other Japanese Americans, the Sakane family enjoys the freedom and liberty offered by their home.