lengthy stuff
History:
Chibiusa is the daughter of Neo-Queen Serenity and King Endymion, the 30th century versions of Sailor Moon and Tuxedo Mask. Like them, Chibiusa has an extended lifespan of about one thousand years, but for most of that Chibiusa remained physically and mentally about five or six years old. No one could figure out why, but King Endymion theorized that it was because of her blood - she was the result of the first union between a human prince and a princess of the White Moon, so much is unknown of how that genetic makeup changes one's physicality from a typical human. After several centuries of remaining unchanged, the people of Crystal Tokyo began spreading rumors that Chibiusa wasn't the real Princess. Chibiusa, whose only friends were Sailor Pluto, her Guardian-in-training and talking kitten Diana, and her Luna P Ball, decided that she would prove to everyone (and herself) that she WAS her Mama's daughter. She went into the Queen's sacred chamber and stole the Ginzuishou from its shrine and place of honor. But the Ginzuishou was the world's defense, and without it in the right hands or in its place, anything could happen.
And so the Black Moon happened. The Black Moon clan were a bunch of criminals, a rare breed in the utopia of the 30th Century, who had decided to follow Wiseman. Wiseman had been a horrible criminal and murdered many people; he was banished to Nemesis, the negative energy planet hidden far beyond the Solar System. When the Black Moon attacked by hurling enormous monoliths of their Black/Dark Crystal, the devastation was astronomical. Those who didn't die from the explosions later faded and died from a mysterious plague emanating from the Crystals. Even the Palace wasn't spared; the Queen had run out to defend the city, but her body had been completely encased in crystal the instant the monolith hit the Earth, and she had been sleeping (or dead?) in the crystal since. The King and the Queen's Guardian Senshi took the worst of the blow, and were all sent into comas. Chibiusa and Diana alone were unharmed, and the guilt for what she had done weighed heavily. Diana refused to leave her parents, Luna and Artemis, but Chibiusa resolved to get help. The King had told Chibiusa many stories about the legendary invincible soldier, Sailor Moon. So Chibiusa went to the Time Gate and stole a Time Key from Sailor Pluto, then broke the laws and went back into the past, to the 20th Century.
Chibiusa landed on top of Usagi and Mamoru, and proceeded to disrupt their lives. She was rude and demanding, pulling a fake gun on Usagi to intimidate her into giving up the Ginzuishou. She hypnotized Usagi's family in order to keep an eye on Usagi, and was generally bratty. But it was quickly obvious that Chibiusa was a lonely and misplaced child, and also that she knew more about Sailor Moon and the Senshi than a random little girl should. Though she claimed her name was also Usagi, Mamoru came to calling her Chibiusa to differentiate the two.
But Chibiusa wasn't safe here; the Black Moon had followed her, looking for the Ginzuishou she had stolen. Their method of attack was to capture the Senshi, one after the other. Chibiusa stole Usagi's transformation locket, therefore causing Usagi to not transform in time to save Sailor Jupiter. Usagi demanded a reason for the theft, and Chibiusa finally revealed that she was from the 30th Century, and begged for Sailor Moon's help. So Sailor Moon, Sailor Venus, Tuxedo Mask, and Chibiusa all travelled to the future.
(...I'm going to start editting. This is too damn long, and every detail really isn't that important |Da)
They met Sailor Pluto briefly, where Chibiusa apologized for deceiving her and stealing the Time Key. Then they stepped through the Time Gates and saw a ruined Crystal Tokyo. When they reached the Palace, they found Neo-Queen Serenity sleeping in her casement of crystal. And the spirit of King Endymion appeared. He had found a way to leave his body and came to help, giving the group much vital information. ...Including the identities of himself, the Queen, and their child. (Much hilarity ensued.) After some stuff that I don't remember so well, Chibiusa wandered past the Time Gate and deep into the Fourth Dimension, wanting to get away from everyone because she believed herself unneeded. And Wiseman found her there, and took her. He gave her a false awakening and a false adult body, and she became Black Lady. Black Lady was sent back to the Palace to retrieve Sailor Moon's Ginzuishou. Sailor Moon and the others were shocked to see her like that, and let their guard down enough for Black Lady to grab Sailor Moon's transformation locket. But Prince Diamond stole both of them from her, and threatened to toucu the two to one another - which would surely destroy the universe (ohnoez!). Sailor Pluto disobeyed her orders to always stay at the Time Gate and went to the Palace to make sure everyone was alright, and found the scene of chaos. She broke the greatest taboo and stopped time, for which the cost is her life. She ordered Usagi to retrieve the two Ginzuishou, and a relieved Pluto gave her last farewells. Black Lady had been staring the whole time, and upon Pluto's death, cried. The death of her best friend broke the hold Wiseman had on Chibiusa's mind, and she glowed with a strong light.
Chibiusa had awakened! Her tear, like her mother before her, had become her very own Ginzuishou, and she was transformed into Sailor Chibimoon! So she stayed with Usagi in the 20th Century to train to be a great Senshi.
(...Okay, much paraphrasing now |Da)
Chibiusa befriended Hotaru, a sickly middle schooler whose father Professor Tomoe was one of the main baddies of the next story arc. Tomoe had implanted one of the alien seeds inside Hotaru, and she became Mistress 9. Mistress 9 stole Chibiusa's Ginzuishou and consumed it. But what little spirit was left of Hotaru inside Mistress 9 suppressed its power so that Mistress 9 couldn't absorb all its power, and therefore kill Chibiusa. In the end, Hotaru sacrificed herself to return Chibiusa's Ginzuishou, and became Sailor Saturn, the Senshi of Destruction, and second in power only to Sailor Moon. The whole story arc had the newly appeared Outer Senshi fighting the Inner Senshi over Sailor Saturn; the Outers wanted to kill Hotaru before she awakened, the Inners wanted to save her. So it was thought the end of the world would happen because of Saturn's appearance. But Saturn commanded Pluto (who had been reborn into the 20th Century) to open an inter-dimensional gate; Saturn planned to push the evil Pharaoh 90 into an alternate dimension, and THEN destroy it (and as the price, herself) completely there. And so it was done. But all hope was not lost! Hotaru was immediately reborn; an infant found amidst the rubble. So the Outers took it upon themselves to raise her, and left the group.
Next spring, there was a solar eclipse. The next group of baddies, the Dead Moon Circus, took this opportunity to invade Earth. While watching the eclipse, Chibiusa, Usagi, and Mamoru saw a vision of the Circus' ship descending from the sun (or, to be precise, the dark side of the moon). A few minutes later, a vision of a pegasus appeared before them, pleading for their help before disappearing. That night, the Pegasus appeared in Chibiusa's dream and let her ride his back over the city. She saw a dark spot, which is where the Circus was located. Pegasus gave her a bell with which to call him when in need. In the next battle she did so, and he aided her and Sailor Moon by powering up their transformation brooches and giving them weapons. As time went by, Chibiusa and Pegasus grew closer. At a time where she doubted herself and her worth, Pegasus revealed his true self to her - a young man with white hair named Helios. Chibiusa continued fighting alongside the others, until they reached Elysion, the idyllic heart of the Earth where Helios is the High Priest. He was imprisoned there by the Circus' leader, Queen Nehelenia. After Nehelenia's defeat, Chibiusa feared that Helios was dead. She kissed him in her desperate, silent prayer for him to live. Live he did, and Chibiusa's heart caused her Ginzuishou to evolve into the Pink Moon Crystal.
Chibiusa returned home after this, but not for long; odd things were happening in the 30th Century. Chibiusa resolved to go back and help Sailor Moon, but was quickly killed. She was not revived until Sailor Moon reached the Galaxy Cauldron and wished for everyone to live again. Chibiusa floated away from the others, with the promise that she would see them again. It's assumed she took her place as the new Senshi, with her Asteroid Quartet by her side.
(p-phew ;;;)
Psychology:
It's hard to talk about Chibiusa without mentioning Usagi. Chibiusa is often compared to her, being that they're mother and child. They are both extroverted, excitable, painfully optimistic and naive, child-like and chilish, believe in love and life and friendship, loved by everybody, gregarious...
The truth is, Chibiusa has an enormous inferiority complex regarding Usagi. Or, to be more specific, Usagi as she will be as Chibiusa's mother - Neo Queen Serenity. The queen who rules the world, the most powerful person in the universe, the most beautiful and graceful and beloved and feared in the universe. Chibiusa loves her mother as much as she is afraid of her, as much as she is in awe of her, for Chibiusa's mother is a living legend.
As much as Chibiusa wants to be like her mother, she is her own person. Unlike Usagi, Chibiusa is pretty intelligent and precocious, independent and often almost fearless. Her smarts occasionally results in bossiness, but for the most part she puts it to good use like schoolwork and being class representative. She's popular and has many friends in school.
Also unlike Usagi, Chibiusa has the capacity for hatred. Growing up for 900 years as lonely as she was has had that effect on her, and she's been shown to develop hatred for particularly cruel enemies. Thankfully, after her time as Black Lady and finding out the truth of how loved she is by her parents, Chibiusa started emotionally repairing herself with the love and support of her parents and their friends as they were in the twentieth century, when they were all young and more approachable.
At this time in the manga series, Chibiusa has fully come into her own. She fully believes in herself and her worth as an individual rather than just the daughter of the living legend Sailor Moon. She's also started becoming more centered, strong, and powerful. Having finally evolved her own Silver Crystal and discovering that she has her own Sailor Team, Chibiusa has all the wisdom and strength to be the true Senshi she's always dreamed of being.
Chibiusa is very extroverted, outgoing, and optimistic. She believes in the best of everyone, but her world is somewhat black and white; good people are good, and no matter what their intentions, people who hurt those she cares about are bad, end of story. She's socially awkward in the beginning of her appearance, probably due to the fact that she never had many friends. But once she settles into the routine of 20th Century school life, she becomes very popular, even class rep. Her dream is to be a beautiful lady as great as her mother the Queen, so Chibiusa sometimes goes out of her way to be more adult than she's mentally ready for; doing things on her own and being a little bit of a perfectionist. But really, she's still mentally a child in some ways and very girly; her favorite colors are pink and red, and she almost obsessively collects rabbit items (backpacks, clocks, etc). She's also a huge sweet tooth with pudding as her favorite treat; there's an extra story in the manga that deals with going to the dentist. Chibiusa does on occasion whine loudly when she doesn't get her own way.
There are many similarities between Chibiusa and Usagi. Both love sweets and people, are compassionate and caring, but can also be very childish and demanding. The biggest difference between the two is that Chibiusa is actually intelligent; she does well in school. She can be bossy, especially towards Usagi. Chibiusa is easily vulnerable and has a need for a purpose and individuality within the Senshi group, otherwise she feels worthless next to Sailor Moon. But she is pretty tough, and will do whatever it takes to help others, especially those she cares deeply about. As the manga goes on, Chibiusa grows more confident and mature.