By requiring a password, they ensure that:

to avoid extraction errors common with built-in Windows tools. Copy and paste ryuugames.com carefully; ensure there are no trailing spaces. If an archive is multipart (e.g., .part1.rar .part2.rar

Thus, if you are trying to extract a game downloaded more than a month ago, you will likely need the “UPD” password.

If you receive a "wrong password" error even after entering ryuugames.com , it may not be a password issue at all. Consider these technical fixes: