Japanese Excel tries to read it in Shift-JIS.
So, you need to change your CSV file to Shift-JIS encoding or other types that can be read in Japanese Excel.
This link might be helpful (it in Japanese)
https://d.hatena.ne.jp/replication/20100211/1266232291
This reply must be way too late.. though, I write for forum archives.
I hope you have solved the case.
