Yes. Gijinka does not mean it has to be pokemon or digimon or any show or whatever. Gijinka just means a humanized version of something that was initially not human. Like, you can make a gijinka of anything really. I've even seen people make them based on cell phones and computers. XD But if you make a gijinka based on something copyrighted, like pokemon, then it is technically a "fan character." It's still an OC, but as you don't own the rights to pokemon characters, the OC falls in a weird grey area.