This is the 9250th most frequent Japanese word.
由貴
"由貴" is a Japanese given name meaning "reason, origin" (由) and "precious, valuable" (貴).
In this sentence, "由貴" represents a proper noun, specifically a person's name. It is treated as the subject of the sentence.
由貴さんはとても親切な人です。
Ms. Yuki is a very kind person.
Here, "由貴" again serves as a proper noun indicating the name of an individual (the author mentioned).
この小説の作者は由貴さんだそうです。
The author of this novel is said to be Ms. Yuki.
In this usage, "由貴" is referenced as a name in general, discussing its popularity as a given name.