I am the person that will be helping you today.
You can change it back to English by following the instructions found on this page: https://www.youtube.com/watch?v=xaHtr243Prs
The words on your Kindle will be different because it is using Japanese, but all the items that you need to choose will be in the same locations.
I look forward to hearing your feedback concerning whether or not your problem is fixed.
I hope to hear back that all is working. If this is so, please do not forget to rate my help on the top of this page (choose the number of stars and click the Submit button). If it is not, please respond below.
I will be standing by,Jason