With a hybrid there are more options but the era should be kept in mind.  If something western is in the scene then it should have a reason for being so far from home.  Anything from exile by a powerful lord to a summoning spell gone wrong would work to relocate a western zone character or factor into an eastern area.  But, I do believe that the setting should be predominantly eastern with ... dare I say... western sprinkles?

Also, given the intense zealotry associated with any form of forced group identification, it might be wise to incorporate something more akin to a talisman rather than a brand.  This talisman would be worn in a similar manner to an earing or other accessory and would cause an identifiable physical characteristic to be more spirit-like than human-like.  Depending on the spirit, they might choose something that they feel is a more attractive feature like their ears, fins, hair, etc.

Furthermore, the hunting of spirits could be limited to those who dwell or linger within human settlements without a talisman.  Basically, they need to be honest in introducing themselves in order to be respected.  Even in our age, which is far less strict than before, failing to introduce yourself or lying about your identity is a deal breaker for both personal and business relationships.  Given the odds of humans being on the losing end of such deception, the government would be failing to do its duty if it did not take some action to protect its people from duplicitous non-citizens as well as encouraging honest and well intentioned non-citizens to become citizens.

However, this is all brainstorming, really.