If you are looking for a portable version to use on a tablet or laptop, these are the authorized methods:
Japanese From Zero! (5 book series) Kindle Edition - Amazon.com japanese from zero book 1 pdf google drive portable
For those who prefer digital copies or need a portable version, "Japanese from Zero" Book 1 is available on Google Drive and other online platforms. A simple search will yield several results, including PDF versions of the book, workbook, and audio files. If you are looking for a portable version