Here's her story:
''Princess Hikari— “Sailor Moon Fighter” is a result of an illicit love affair between Neo Queen Serenity and Seiya whilst they were visiting on Kinmoku. After they parted and Serenity returns to Earth, she discovers she is pregnant with Hikari. Since both Seiya and Endymion shared similar hair and eye coloring, Hikari looked close enough to Endymion that no one questioned her parentage.
When Empress Kakyuu and her Starlights visit Earth several years later for Chibiusa’s coronation and marriage to Helios, Seiya quickly realizes that he is Hikari’s biological father. This is undeniably confirmed when she awakens as Sailor Moon Fighter.
Hikari herself is very mature and perceptive for her age. Even though she felt she never quite fit in especially with Endymion and her role as princess, she always tries her best to never disappoint, and is a bit reserved. She actually shares a very close relationship to her half-sister, Chibiusa to whom she always looked up to. It was in trying to protect her elder sister during the coronation that caused her to transform to “Moon Fighter” and much to her deep regret resulted in causing a rift between them as it revealed her true parentage. Eventually, she leaves with Usagi and Seiya to traverse the universe after Usagi separates from Mamoru on mutually amicable terms. (especially after both parties feel that they've fulfilled their destiny, the well being of Crystal Tokyo is secure with Chibiusa, and they are both finally free of obligations)
Despite finding happiness with her new family, she always felt unwavering loyalty to Chibiusa and eventually returns to Earth—not as a Princess, but to serve as one of the new Queen’s Senshi, and the two reconcile. Even further down the line, she will become close friends with the fairy, Perle (Peruru). Hikari’s name means “light.” ''
Senshi Maker: www.dolldivine.com/sailor-moon…