CSV files often display garbled text because the file encoding (UTF-8) does not match the encoding that your version of Excel uses to read files (Shift-JIS).
Please try opening the file using the method described in the manual below and check if the issue is resolved.
How to open a CSV file in Excel without garbled text
Windows: https://teachme.jp/8/manuals/4881129
Mac: https://teachme.jp/8/manuals/4890560