Yuna is the main character of the series. At first, she was just another normal schoolgirl: a first-year student at Yokohama's Shiraokadai All-Girls' High School, enrolled in class 1-B, commuting from home to school each day via the local train route. Sometime prior to the first game, Yuna and several other girls entered the "Miss Ojousama Contest", an intergalactic beauty pageant, with Yuna herself being chosen as the winner. In doing so, she became an instant celebrity, and began a career as a popular idol singer.
One night, the Matrix of Light Elner appeared to Yuna. She introduced herself as part of Yuna's personality (literally translated, "her other self"), and asked her to become the Savior of Light. Yuna then learned a great evil was about to invade the universe, and that Yuna herself had been charged with its protection. Thus began the first of Yuna's intergalactic adventures.
Yuna is sometimes a bit clumsy and prone to making silly mistakes, and at first glance, one would think she's a natural airhead. However, she has a very energetic and positive personality that more than makes up for her shortcomings. She isn't very skilled as an idol singer, nor is she quite diligent in her studies and exercise routine, and both her enemies and friends often wonder whether she has any potential talent that has yet to be unlocked.
During battle or times of great personal danger, Yuna undergoes a henshin sequence and appears wearing her armored battle suit, the Light Suit. Her Light Suit has a very large array of weaponry to use in her battle against the forces of evil, ranging from a sword and rifle to an incredibly powerful beam cannon called the Matrix Divider (In "Galaxy Fraulein Yuna 2: Eternal Princess", it is upgraded to a more powerful version known as the Matrix Divider Plus).
Yuna is also a HUGE fan of the TV superheroine Ojousama Kamen Polylina (or Polylina the Masked Maiden), proudly boasting her status as "the #1 fan of the "Polylina-sama Fanclub". This fandom borders on complete obsession, with Yuna even going as far as referring to Polylina as her "one and only". Her heroine is in fact a TV character played by her best friend Lia, but for some reason, Yuna NEVER manages to figure it out. In fact, Yuna's affection for Polylina is a major running joke in the series, with Lia often reacting in some (usually humorous) fashion to Yuna's fangirlish (and somewhat misguided) proclamations of shōjo-ai for her idol.
Her friends call her by a variety of nicknames, including "Yuna", "Yuna-rin", and "Yuna-san". Yuna Kagurazaka currently lives with her parents, Naoko & Yuuichiro Kagurazaka, on Earth, in Japan's Yokohama Prefecture.