Slavery means people are not remunerated and have no personal freedom. Japanese are definitely remunerated and definitely have personal freedom.
"お疲れ様でした" (otsukaresamadeshita) = "Thank you for your hard work".
Japan takes great pride in work. Just because you don't understand the culture doesn't give you the right to call it slavery.
If you want to invoke a discussion on slavery in East Asia, do it in the right context.
https://www.forbes.com/sites/ewelinaochab/2020/04/04/the-fat...