She is an original female character who obviously serves as an idealized version of the author mainly for the purpose of Wish Fulfillment. She's exotically beautiful, often having an unusual hair or eye color, and has a similarly cool and exotic name. She's exceptionally talented in an implausibly wide variety of areas, and may possess skills that are rare or nonexistent in the canon setting. She also lacks any realistic, or at least story-relevant, character flaws — either that or her "flaws" are obviously meant to be endearing.
She has an unusual and dramatic Back Story. The canon protagonists are all overwhelmed with admiration for her beauty, wit, courage and other virtues, and are quick to adopt her as one of their True Companions, even characters who are usually antisocial and untrusting; if any character doesn't love her, that character gets an extremely unsympathetic portrayal. She has some sort of especially close relationship to the author's favorite canon character — their love interest, illegitimate child, never-before-mentioned sister, etc. Other than that, the canon characters are quickly reduced to awestruck cheerleaders, watching from the sidelines as Mary Sue outstrips them in their areas of expertise and solves problems that have stymied them for the entire series.
Huh, Nozomi fits that description pretty well
this character is completely irreverent to be because i don't watch shoninshit programming