Neito was born into the Royal Nobility of Naranai. Once he reached four years of age he was given a shiny Vulpix named Burūfokkusu as a protector. At the age of seven he began to learn royal combat and mastered it at the age of Twelve. One year later he received the royal crest to signify his claim to the thrown and his ascent into his teen years. When he reached sixteen his Vulpix was evolved to a Nintails. Two months after his sixteenth birthday the Kings younger brother forced a Coup D'Etat onto the king and was successful. Once the brother became king, he issued a decree stating that the previous king and all of his family were to be executed. After hearing this the former king gave his sward, Nibuidesu, to Neito along with a healthy sum of money and told him to run. Since then Neito has been wandering from country to country fighting anyone he views as corrupt.
So 50 years ago the Xuirong region got destroyed and all the inhabitants fled to Argent thus becoming migrants/refugees mostly in the city while the rest of the locals spread themselves around the country. Because of this I assume that most of your Royalty history would be up in the air at the moment since you are not of Argentian decent and I doubt that an immigrant would be able to become a member of the royal family so quickly.
Other than that, I don't see any other issues with the character. Just need to work on a new back story as such. Refer back to the OP and have a re-read so you know you're not missing any other important details.