Audience Surrogate Newcomer

In short, Supporting Protagonist meets Audience Surrogate.

There's some world that is already happening, and this character gets thrown in, in medias res, which is an awful lot like Real Life can be. They're not really privileged above any other character, but they give the audience someone to follow.

Anime and Manga

 * Kagome in Inuyasha

Live-Action TV

 * Noah Wylie's Dr. Carter in ER
 * Harry Kim in Star Trek: Voyager