Suggestion for resetting retainer class

[Nyalia]

As others have said, you need to unequip your retainer's gear before you can reset their class, no matter how many yes prompts you click.

Yeah, the only time it's actually a danger is when you're getting ready to use Retainer Fantasia (or have just used it), which also requires you to remove all your retainer's gear (I guess in case you change their race or gender while wearing race/genderlocked stuff). But even then, there are a few warning boxes you have to click yes to.