I'm just really bad with coming up with last names, honestly I just slapped Walker on last second. However, in my head she took the last name of her adopted father whose family originally came from the west. He was born and raised in Japan and became a police officer and because of his spiritual abilities he transferred to the Imaginary District were he met his wife, who was also on the force. They married but couldn't have children so they looked into adoption. Well I can just change it to have a Japanese name, maybe Fujiwara.

Also she was either lost, separated, abandoned or whatever by her birth parents for a short time and was taken in by cats or maybe some stray dogs, idk it seemed pretty funny in my head but I can change it, if doesn't make sense.

About her sword training, I can ditch that for just marshal arts training.