Guilty Crown: The Lost Kingdoms is a retelling of the Guilty Crown series with the five magical girls from Puella Magi Madoka Magica as AU guests. It somehow averts the tropes use in typical crossovers, and serve as a movie fic with nine chapters.
The setting is also a stand-alone AU of a notorious fanfic franchise called YuYuGiDigiMoon, in which the outbreak of Lost Christmas (taking place in December 2012 instead of 2028 to coincide real-life predictions) wiped out most of Japans heroes. This serves as a background and new plot twists unlike the show for the characters to interact in dark times.
Stories:Guilty Crown: The Lost Kingdoms - The main story itself.
Guilty Crown: The Lost Kingdoms - Gaiden - A collection of sidestories. Not really required reading, but still worth a look.
House of Madoka: Halloween Night - Non-canon. A co-authored character corner/theater that converts to a humorous story about a Halloween party at New York City with various crossovers of pop culture. The characters of GC: Lost Kingdoms made guest appearances.
Guilty Crown: The Lost Rebellion - An alternate ending of the story that is M-mature.
The Devils of Cocytus - An M-mature pairing story of Homura Akemi and Mana Ouma.
''The Ningyo and Her Legs' - An M-mature pairing story of Ayase Shinomiya and Sayaka Miki.
This fanfic provided examples of:
- Ancient Conspiracy: Da'ath is one, in which Yuu revive the organization for his own purposes.
- Apocalypse Maiden: Mana/Inori are set to become one further with the powerful phoenix force inside her.
- Ascended Extra: Kenji Kido is a protagonist. Argo has an active role in Ayase and Tsugumi's level. Even Shibungi and Oogumo.
- Bittersweet Ending: Although Da'ath and GHQ are defeated in the final chapter, Shu and Inori sacrifice themselves to save the universe by removing the Apocalpyse Virus in existence.
- Colony Drop: Like the anime, the Leukocyte is about to crash to Tokyo. It took Shu to combine Inori, Kenji, and Mami's voids to destroy it, resulting in fireworks afterward.
- Crapsack World: A world without superheroes, alongside GHQ controlling the country.
- Lighter and Softer: Though it still has its dark moments, its more of a reconstruction of Guilty Crown and Puella Magi Madoka Magica at times.
- Early-Bird Cameo: In chapter 1, it shows certain characters such as Segai, Arisa, and even Kenji appear early than in the show.
- Our Dragons Are Different: In chapter 3, Lokis minions has four dragons that serve the trickster-god. Later on, GHQ/Da'ath has Malefic Dragons from Yugioh.
- La Résistance: Funeral Parlor, but there is also a diversity besides humans consist of demons from Makai and a reptilian race called the Rajita.
- Shout-Out: Throughout the setting, the fanfic transitions the themes like in the anime. The early chapters have a few shonen traits at times and tributes to anime from the 90s to the 2000s. The later chapters focuses drama, quality obviously gets better, and focus more on the anime 2010s onward.
- Gai's nickname, Gairyuki, references a Zoid. It is less mentioned in later chapters though.
- Hirohide Nanba becoming an antagonist later on references GuiltyKingOumaShu's fanfic, Reclaiming the Throne, where Nanba has a major role of being evil.
- In the final chapter, it is revealed that there's a Guilty Crown multiverse concept with mentions of the canon anime, Reclaiming the Throne, Vuken's Shackles of Guilt, MaeBleu's Guilty Melody, and LukeLC's stories. Basically, Guilty Crown: The Lost Kingdoms is like the Aligned universe of Transformers.
- Spared by the Adaptation: Oogumo who died in Episode 19 of the anime survives in this fic. In chapter 2, Kyo (the girl appeared in episodes 2-6 and dies) is seen alive and well. In chapter 6, Ritsu Takarada lives.
- The Virus: The Apocalypse Virus. Apparently, it has stronger effects that wipe out most of Japan's heroes such as the Sailor Senshi and Spirit Detectives.