While there's a copy:saiyuki tag for the manga/anime franchise, there's also a need for a 'general' tag of some sort to denote crossovers I guess. I think I'd prefer general:journey_to_the_west, but it's fine as is.
Yeah, I don't know if it really counts as a "copyright", as it is not subject to copyright (hella old). However, it's certainly not a character, nor is it an artist, and it is a "storyline" from which characters come, much like most other tags marked as copyright tags. That's why I set the tag as copy:journey_to_the_west, but of course you're welcome to change it to general if you like.