With the Star Seeds back to their hosts and Chaos in its whereabouts, Sailor Moon and the Sailor Senshi have brought the Earth back to its light as well as the Silver Millennium of the Future. But there was another kingdom that no one has ever heard of... a kingdom that glistened in the stars.
The Celestine Millennium glittered in the galaxies' light as it stood boldly beyond the Moon, over thounsands of years ago. Queen Stella and her young son, the Prince of the Celestine Millennium had ruled the kingdom with great power, but with a gentle and graceful heart. But then one day, the Celestine Millennium was invaded by King Rhodonite. Holding a great dark power, he raided through the Millennium, killing everyone who stood before him. Like, how Queen Serenity did when the Moon Kingdom was invaded, Queen Stella used the Iridescent Star Crystal to defeat Rhodonite. However, the kingdom wasn't so lucky and neither was the Prince.
After the heartbreaking battle, a young boy named Hoshimiya Takeru meets a young wolf named Silver who tells him that he is one of the chosen warriors: the Crystal Knights and that he must awaken the other Crystal Knights and find the Iridescent Star Crystal to revive the Prince.
With school lurking around him, Can Takeru accept his destiny as a Crystal Knight while dealing with school at the same time?
Hoshimiya Takeru (星宮尊 Hoshimiya Takeru?) / Starlight Knight (スターライトナイト Sutāraito Naito?)
Takeru is the main protagonist of the series and leader of the Crystal Knights. Like Serena (Usagi), Takeru is a klutz and often comes in late for school, earning him a scolding from his teacher. He is smart and excels in his classes, but he's very poor in Mathematics. Takeru is shown to have a very kind heard and cares about peoples' lives other than his own and is talented in drawing manga. He currently lives with his mother after the passing of his father before the series started. Takeru transforms into the Starlight Knight in Chapter One, and his powers are based around the stars. His gemstone is the Amethyst.
Aomori Daisuke (青森大輔 Aomori Daisuke?) / Sapphire Knight (サファイアナイト Safaia Naito?)
Daisuke is the second the main protagonists of the series and the second Crystal Knight to be awakened. He is in the second year in high school and he is shown to be very gentle and calm. He is the vice-president ot the school council and is very responsible at doing most of the tasks. He's very studious and gets the highest grades in his classes like Amy (Ami), and often does study sessions with others. Daisuke lives by himself since his parents are overseas and misses them a lot. He transforms into the Sapphire Knight in Chapter Three, and his powers are based on water. His gemstone is the Sapphire.
Honoshiba Ryou (炎柴涼 Honōshiba Ryō?) / Ruby Knight (ルビーナイト Rubī Naito?)
Ryou is the third protagonist of the series and the third Crystal Knight to be awakened. Ryou tends to be a very serious young man, but deep inside he is just a friendly average young man who is very hard-working. Like Raye (Rei), Ryou lives in Akamine Shrine, and often meditates when not having anything to do. Ryou shows to value his friendship with Takeru and the others, although sometimes he bickers with his teammate, Ikazuki Hikaru. He can be strict when it comes to school work and would often get on Takeru, Joushirou, and Hikaru to study which could sometimes be a peeve to the three. He transforms into the Ruby Knight in Chapter Six and his powers are based on fire. His gemstone is the Ruby.
Fuuma Joushirou (風魔条詩郎 Fūma Jōshirō?) / Emerald Knight (エメラルドナイト Emerarudo Naito?)
Joushirou is the fourth protagonist of the series and the fourth Crystal Knight to be awakened. Joushirou or Joey is the tallest member and has a strong sense of justice. After the loss of his parents, he was raised by his grandparents until he was old enough to live on his own. Joushirou maybe tough on the outside, but is very compassionate on the inside, not to mention having a habit of picking up small stray animals. He is a very skilled cook like Lita (Makoto), and would often share his food mostly to cheer people up. He transforms into the Emerald Knight in Chapter Nine and his powers are based on wind. His gemstone is the Emerald.
Ikazuki Hikaru (雷瀬ひかる Ikazuki Hikaru?) / Diamond Knight (ダイヤモンドナイト Daiyamondo Naito?)
Hikaru is the fifth protagonist and the fifth and last Crystal Knight to be awakened. Hikaru is very handsome and is very popular with the girls, but he is shown to be very happy-go-lucky and a bit clueless at times. Unlike the other Knights, Hikaru was awakened like how Mina (Minako) was awakened as Sailor Venus. He is also shown to be bad at his studies and would often get chewed out by Ryou, which explains why they butt heads sometimes forcing to have Takeru intervene. He transforms into the Diamond Knight in Chapter Twelve and his powers are based on lightning. His gemstone is the Diamond.
Silver (シルバー Shirubā?)
Silver is one of the allies that is one of the mentors of the Crystal Knights. Silver is a light-gray wolf who lived in the Celestine Kingdom, who was also guardian of the Prince. He's shown to be very humble and loyal and is ready to battle, whenever a threat occurs, but whenever nothing is going on, Silver tends to be very laid-back and often sleeps. Although, Silver is a wolf, his true form is a human and he often changes to his real appearance whenever he wants as well as having a human name, Shirogane Seiji (白金清二 Shirogane Seiji?). He appears in Chapter One, when he discovers Takeru and his incredible power lingering around him.
Seioh Ayaka (聖王絢香 Seiō Ayaka?) / Sailor Earth (セーラーアース Sērā Āsu?)
Ayaka is a mysterious girl who Takeru meets in Chapter One, when he accidentally bumps into her. She is shown to be friendly to Takeru and the others, and it is revealed that she is a legendary warrior: a Sailor Soldier named Sailor Earth who was part of the Celestine Kingdom before King Rhodonite attacked. Ayaka has been fighting Rhodonite's generals and monsters right before the Knights were awakened and she was given the duty to aid them into their battle for the Earth's protection. Her element is nature and her gemstone is the Turquoise
Koganezaki Shuuichirou (黄金崎秀一郎 Koganezaki Shūichirō?)
Shuuichirou is a teacher who mysteriously transfers into Takeru's high-school. Although mysterious, Shuuichirou or "Kogane-senei" is shown to be very humble, good-natured and friendly towards the Crystal Knights. He is very popular with the girls and would often be given love letters and even get confessed, but he actually has romantic feelings for Takeru which starts to progress throughout the series. He knows about the past of the Crystal Knights and their present identities.
- King Rhodonite (キングロードナイト Kingu Rōdonaito?)
- Amethyst Star Amulet (アメジストスターアミュレット Amejisuto Sutā Amyuretto?): The Amethyst Star Amulet is a brooch-like item introduced in the first chapter of Crystal Knights. It was given to Takeru by Silver, allowing him to transform into the Starlight Knight by raising the Amulet up in the air and shouting the phrase, "Star Amethyst Power, Knight Up!" and the gemstone, the Amethyst corresponds with him. Takeru carries the Amulet with him advised by Silver because he will never know when Rhodonite's generals will strike.
- Golden Jewel Amulet (ゴールデンジュエルアミュレット Gōruden Jueru Amyuretto?) : The Golden Jewel Amulets are the magical transformation items introduced in the Crystal Knights chapters. Like the Amethyst Star Amulet, the Golden Jewel Amulets are brooch-like items used by the primary Crystal Knights. Each Amulet has a respective gemstone corresponding with the Knights: Sapphire (Daisuke), Ruby (Ryou), Emerald (Joey), and Diamond (Hikaru). To transform, the boys use their transformation command as they raise their Amulets into the sky.
- Turquoise Earth Prism (ターコイズアースプリズム Tākoizu Āsu Purizumu?) : The Turqouise Earth Prism is a transformation brooch introduced in the thirteenth chapter of Crystal Knights. This item allows Seioh Ayaka to transform into Sailor Earth by saying the phrase, "Gaia Prism Power, Make Up!" and the gemstone, Turqouise corresponds with her present self as well as her past self. When not in use, Ayaka wears her Earth Prism on the bow of her school uniform.