Rini

"Silver Crystal, please give me the strength to protect my friends."

- Princess Rini, ep. #82

Rini (ちびうさ), born Serena Tsukino, is the daughter of Neo-Queen Serenity and King Darien, and a protagonist in Sailor Moon. Born during the 30th century, Princess Rini was sent back to 20th Century by her protectors, Sailor Pluto and the Sailor Scouts, to prevent her capture by the Negamoon Family. In the past, Rini attempts to find the Imperium Silver Crystal to save her mother and father from the Negamoon. After her family and future is rescued, she becomes Sailor Mini Moon and aids Sailor Moon and the Scouts in the 20th Century against the Bureau of Bad Behavior and Queen Nehelenia's Amazon Trio and Quartet.

Negamoon Arc
Shortly after passing through the Door of Time and Space, Rini lands in the 20th Century, interrupting Serena Tsukino and Darien Shields' date.

She brainwashed Serena's family into thinking she was her cousin. However, the intervention of Luna prevents Serena from falling under the influence of Rini's magic and she is the only one among the Tsukino's who are aware of Rini's nature. When Darien begins to experience nightmares of Serena's demise in the event of their marriage, Rini capitalizes on Darien and Serena's break up and spends most of her time with him. The break up and Rini's presence causes friction between Darien and Serena's shaky friendship. Meanwhile, Rubeus and the Negamoon Sisters attempt to capture Rini whenever the opportunity presents itself. Rini tries several times to return home using the Crystal Key, exposing herself and her dormant power from the Moon to Wiseman's group. Serena and the other Sailor Scouts protected Rini from the Negamoon sisters, Serena and Rini grow to learn to appreciate each other more as time progresses.

In Episode 27, Rubeus Strikes Out, Rubeus captured the other Sailor Scouts and told Sailor Moon to hand over Rini. In the previous episode, Rini discovered that Serena and her friends were the Sailor Scouts and had possession of the Imperium Silver Crystal. When Rubeus captured the other Sailor Scouts, Rini and Serena reluctantly worked together to save them from Rubeus after Rini stole Serena's broach. As Sailor Moon was in a beam struggle with Rubeus, Rini destroyed the crystal that was his source of power, causing Rubeus to be hit by Sailor Moon's Moon Scepter Elimination. Using Sailor Teleport, Serena and the others manage to get Rini off the ship as it exploded, killing Rubeus.

Becoming Wicked Lady
After fighting off several of Emerald's Negamoon monsters, the Sailor Scouts, Tuxedo Mask, Luna, and Artemis traveled into the future with Rini. In Episode 37, Jealousy's Just Reward, it is revealed that Rini took the Imperium Silver Crystal of the future, which then vanished. Sailor Moon tried to awaken Neo Queen Serenity (her future self) with the Silver Crystal of the past, but it did not work, so Rini ran off, where she encountered Wiseman, who convinced her that Sailor Moon, Tuxedo Mask, and the other Sailor Scouts did not love her, and transformed her into Wicked Lady.

Wiseman's intent was to use Wicked Lady to open the dark gate and send dark energy through her to destroy the world, even though she would be destroyed in the process. However, Serena and Darien were able to convince Rini that they did love her. They were, through strict parenting, trying to teach her how to be a more well-behaved princess and future queen. Thanks to their efforts at showing Rini that Wiseman had filled her with false truths and they still loved her very much, Rini became herself again. Wiseman, furious at losing his pawn in the young future princess, attacked them, and entered a power struggle with Neo-Queen Serenity.

When Serena was about to lose, the Imperium Silver Crystal of the future appeared, having gone into Rini's body when it disappeared for protection, so she used it to transform into Princess Rini. Together, both Silver Crystals were powerful enough to decimate the Dark Crystal, as Serena and Rini destroyed Wiseman with an energy explosion. Afterward, Rini returned to the future, which, with Wiseman's death, was restored to normal, and reunited with her family.

Sailor Moon S
When Eugeal began extracting people's Pure Hearts, Rini returned, now with the ability to transform into Sailor Mini Moon using the Prism Heart Compact and saying "Moon Prism Power". She attacked by using the Pink Moon Stick to use Pink Sugar Heart Attack, which sometimes had a delayed reaction, and did not do much damage, but was often a good enough distraction for Sailor Moon to destroy the Daimon.

Rini became friends with Doctor Tomoe's lovely daughter, Hotaru Tomoe. She and Sailor Moon were determined to save her from Mistress 9 when they found out she was possessed by her, and tried to stop Sailor Uranus and Sailor Neptune from killing her. While the Sailor Scouts were fighting Cyprin and Petirol, Kaorinite captured Rini and took her to feed her Pure Heart to Mistress 9, allowing her to awaken. It was eventually returned to her by Hotaru after she destroyed Mistress 9 and turned into Sailor Saturn.

Following the defeat of Pharaoh 90, Rini returned to the future, but came back to help the Sailor Scouts defeat the final Daimon, Rangy.

Sailor Moon Super S
In the first episode, Rini began having dreams about Pegasus. It was her that the Dark Moon Circus was searching for, but they did not know it yet. Hebihanabiko, the Remless, entered Rini's dreams through Pegasus in an attempt to convince her to use his power to rule the world, but she refused, and Sailor Moon destroyed Hebihanabiko.

She also gained the ability to transform into a Super Sailor Scout using the Crisis Mini Moon Compact and by saying "Moon Cosmic Dream Action" with Serena. By using the Crystal Chime and saying, "Crystal Twinkle Bell", Super Sailor Mini Moon could summon Pegasus and enable Super Sailor Moon to use her new finishing move, Moon Gorgeous Meditation.

When Super Sailor Mini Moon summoned Pegasus so that Super Sailor Moon could defeat the Amazon Quartet, Queen Nehelenia realized that she was the holder of Pegasus, so Zirconia used Zircon to extract her dream mirror (the golden mirror), and trapped her inside Nehelenia's mirror. Nehelenia made Pegasus become Helios again and took his Golden Crystal, putting Super Sailor Mini Moon into eternal sleep unlike Queen Beryl's general, Jedite's.

Helios woke Super Sailor Mini Moon up from eternal sleep with the last of his power, and she used the Golden Crystal (once it was taken from Nehelenia by the Amazon Quartet, who by now had switched sides) to talk to everyone on Earth and say "Moon Cosmic Dream Action" to restore the Golden Crystal's power.

Super Sailor Moon and Super Sailor Mini Moon then defeated Nehelenia with a gold energy beam from the crystal, but she survived and kidnapped Super Sailor Mini Moon, throwing her over the edge of the circus tent as it drew closer to the Dark Moon. As Super Sailor Moon jumped off after her, Nehelenia returned to her mirror. Helios turned into Pegasus and turned Serena and Rini into their princess forms with wings to save them from the fall. Afterwards, Rini said goodbye to Helios, with the Amazon Quartet providing a well-timed distraction for Rini and Helios to have a private moment before he returned to Elysion.

Trivia

 * "Rini" is said to be diminutive of "Serena" as "Chibusa" is to "Usagi".
 * "Rini" is said to be Japanese for "Little Bunny". Other sources cite that "Rini" is Dutch and derivative of the name "Katarina".