Jquery datatable exporting to csv problem with other language

I have a Japanese characters in my table. If I use excel button for exporting, it works fine but when I do for CSV. The data or the texts is not correct anymore. Do anyone know how to fix this? Thanks.

Here is my table

And for exporting to CSV and excel

I just used the simple way of creating the buttons for export

                buttons: [
                      {
                      extend: 'excel',
                      text: 'Export to Excel',
                      className: 'btn btn-default',
                      exportOptions: {
                          columns: ':not(.notexport)'
                      },},
                      {
                      extend: 'csv',
                      text: 'Export to CSV',
                      className: 'btn btn-default',
                      exportOptions: {
                          columns: ':not(.notexport)'
                      },}
                    ],