"Pretty Guardian Sailor Moon" is a Japanese tokusatsu superhero series based on the manga by Naoko Takeuchi. It aired from 2003 to 2004 and both adapted and expanded the "Dark Kingdom" arc of the manga. This fanfic is a direct sequel to that story.
Below is a full summary of the show's one and only season. If you've never watched "Pretty Guardian Sailor Moon", consider this chapter a primer for this fanfic. If you've seen the show, skip to "Act 1" instead.
Spoilers ahead.
Usagi Tsukino is a clumsy, lazy, but cheerful and good-hearted middle school girl. One day, she encounters a talking plush cat named Luna, who awakens her as Sailor Moon, the Guardian of Love and Justice. Usagi reluctantly accepts her role to fight the monsters that plague Tokyo. Luna entrusts her with an important mission: find and awaken her fellow Sailor Guardians and protect a hidden princess.
Usagi befriends several girls who later become her fellow Sailor Guardians. Ami Mizuno becomes Sailor Mercury. Ami is a shy, intelligent girl who is lonely. She finds friendship with Usagi and the other Guardians. Her fondest wish is to follow in her mother's footsteps and become a doctor.
Rei Hino is Sailor Mars. She is a powerful shrine maiden with psychic abilities, who is serious and withdrawn. The death of her mother when she was young, and her strained relationship with her absent father, have made Rei reluctant to form meaningful bonds.
Makoto Kino becomes Sailor Jupiter. She is a strong but kind-hearted girl who feels isolated because of her strength. She has a strong feminine side and loves to cook, but people often judge her based on her physical prowess.
Minako Aino is an idol who, in secret, operates as the vigilante Sailor V. She later reveals herself as Sailor Venus and the leader of the Guardians. She has a strong sense of duty and harbors a dark secret. To protect the princess's identity, she impersonates the hidden princess when she first encounters the other Guardians. She also has her own plush cat adviser, Artemis.
Usagi encounters Mamoru Chiba, a young man with whom she forms an adversarial relationship. Unbeknownst to Usagi, Mamoru also prowls the night as Tuxedo Mask, a jewel thief who seeks to restore his lost memories. Tuxedo Mask often helps Sailor Moon in her fights against monsters called youma.
The group of girls makes the local karaoke club Crown, their secret headquarters. The kind and turtle-obsessed Motoki Furuhata runs Crown. He also is Mamoru's best friend.
A hidden group of villains called the Dark Kingdom reveals itself to be behind the attacks on the people of Tokyo. They send youma to gather human energy and try to find the Silver Crystal, a powerful artifact linked to the hidden princess. Queen Beryl leads the Dark Kingdom. Her four generals, Jadeite, Nephrite, Zoisite, and Kunzite, carry out her plans.
Ami continues to struggle with insecurities in her friendship with Usagi and often compares herself to Usagi's other close friend, Naru Osaka. The Dark Kingdom brainwashes Ami during an attack, turning her into Dark Mercury to fight against her friends. She breaks free from the Dark Kingdom's influence and rejoins her friends, but the experience leaves its mark.
Usagi spends more time with Mamoru and falls in love with him. She rejects her crush on Tuxedo Mask. She discovers Mamoru is engaged to be married, but his fiancée breaks off the engagement because she senses the budding affection he has for Usagi.
As their battles intensify, they recover memories of their past lives. The Guardians are reincarnations from a long-dead Moon Kingdom. Usagi realizes she is the princess, Serenity, and her forbidden love for Prince Endymion of Earth, who reincarnated as Mamoru, led to the Moon Kingdom's destruction. Beryl is obsessed with Mamoru, as she long ago was in love with Endymion, as well.
Rei, meanwhile, is the first to discover the true identity of Sailor Venus. They form a contentious bond and clash over their past lives. Rei rejects the notion that her past life's mission must rule her current life. Minako, meanwhile, has dedicated herself to her past life's duty.
Rei also discovers that Minako suffers from a terminal illness. This illness limits the time left to complete her mission, but she continues to fight rather than seek treatment. Minako's duty and sacrifice inspires Rei, who grows close to her.
Usagi's fear of losing Mamoru leads her to transform into "Princess Sailor Moon", a distinct, second personality that emerges when her past self takes control. This dark incarnation possesses massive powers, but grief and anger consume her. It soon becomes clear that it was Serenity who destroyed all things on both the moon and Earth in her grief over Endymion's death. Fearing that history might repeat, Usagi struggles to suppress that part of herself.
Makoto falls in love with Mamoru's best friend, Motoki. At first, she believes her past life demands she stay alone forever, but she eventually opens her heart to Motoki, and the two start a relationship.
Mamoru discovers that Beryl's generals were actually his generals and friends in his past life. He surrenders himself to the Dark Kingdom to rescue them. They regain their memories of their master. Despite Mamoru's best efforts, they perish.
Rei reconnects with her absent father, who is a successful politician. Despite her resentment, she attempts to forgive her father. They forge an uneasy peace. Ami, meanwhile, deals with disappointing her mother, who has noticed that her dedication to her studies has wavered. Ami explains to her mother her goals have not changed, but that her friends also play an important role in her life.
At Rei's urging, Minako gets a risky surgery to fight off her terminal illness and dies during the operation. This shatters the other Guardians, especially Rei, who must now enter the penultimate conflict with the Dark Kingdom without one of their own.
They discover Beryl serves a malevolent force called Metalia, which threatens to destroy the world if released. Mamoru takes this force into his body to contain it, but fails. Instead, Metalia gains control of Mamoru. Necessity forces Sailor Moon to kill him. In her grief, Princess Sailor Moon emerges and attempts to destroy the world. The remaining Sailor Guardians take up arms against their princess and friend to save the world. They fail.
From beyond death, Usagi uses the power of the Silver Crystal, a part of her all along, to restore the world and her friends, including Minako. The Crystal shatters. Mamoru and Usagi remain dead.
Unable to forget Usagi in their restored lives, the former Sailor Guardians will her and Mamoru back into existence. Princess Sailor Moon fades away along with all the Guardians' powers. They can now look forward to a new life together, free from the burdens of their past lives.
Four years later, Mamoru and Usagi are getting married. Ami is studying to be a doctor in America. Rei is honing her spiritual powers. Makoto, still dating Motoki, chases her dream of owning a flower shop. Minako's career is reaching global proportions; she accepts an award as the top artist in Greece.
A servant of the Dark Kingdom, Mio Kuroki, re-emerges to take revenge on the group. A remnant of power from the Moon Kingdom, the Lunar Sword, temporarily restores the Guardians' powers and they defeat their adversary. After their victory, their powers disappear for good.
Mamoru and Usagi get married. Motoki catches the bouquet and proposes to Makoto. The Guardians go their separate ways, each with her own happy ending.
Or so they thought…