I don't understand. Why did the person stay for 10 years? This seems like something you notice after 1 year, or even a few months, let alone 10 years. Is there some family context here that is missing?
At first, you think you're a bit on the outside because you don't know very much and don't speak the language, and you tend to attribute things to your own ignorance.
As you learn more, more and more of the country opens up to you. You make some local friends, you can survive in a small town where no-one speaks English for a few days, and you can have some experiences not available to tourists.
As you learn even more, you notice little slights you didn't notice before -- he gives the example of honorifics. You understand the nuances of comments people make to you. You realize that you'll never be accepted or taken seriously for who you are, you'll always just be an outside.