Kamen Rider Gaim (仮面ライダー鎧武)
Fate/Grand Order: Cosmos in the Lostbelt (フェイト／グランドオーダー：コスモス・イン・ザ・ロストベルト)
Name of the Story
Kamen Rider Gaim: Cosmos in the Lostbelt (仮面ライダー鎧武：コスモス・イン・ザ・ロストベルト)
Synopsis
This story takes place after the events of Kamen Rider Gaim: Epic of Remnant.
Following the completion of Sub-Singularities (亜種特異点) in the previous story, those who threatened the humanity disappeared. Both the ability to Rayshift and the Chaldea's Heroic Spirit Summoning System has been shut down. Chaldea's Servants have departed one by one, leaving only Leonardo Da Vinci (レオナルド・ダ・ヴィンチ) as an acting director.
Haruka Emiya (衛宮 遥河), Ritsuka Fujimaru (藤丸 立夏), and Mashu Kyrielight (マッシュ・キリエライト) were wandering aimlessly at the hallway together as if they will spend their last few days at Chaldea...
However, the Chaldea is under attack and besieged by the unknown organization, conspiring with an unknown entity known as the Foreign God (異星の神), to destroy Chaldea and the current human history, reverting the planet back to the Age of Gods. Haruka, Ritsuka, Mashu, and the other survivors managed to aboard the Imaginary Numbers Submersible Shadow Border (虚数潜航艇 シャドウ・ボーダー) and escape from the facility, rendering the place inoperable and uninhabitable.
In order to save humanity once more, they must travel different timelines dubbed as "Lostbelts" (異聞帯 ［ロストベルト］), an alternate versions of history that differ drastically from the main human history and were "pruned away" from the primary timeline after having been deemed a dead end.
Each of these seven Lostbelts are represented by the Crypter (クリプター), which consisted of the members of Chaldea's Team A, led by its leader; Kirschtaria Wodime (キリシュタリア・ヴォーダイム). The Chaldean survivors will stand up and fight against the Crypters and their Servants for the ultimate fate of human history.
However, Haruka Emiya and Ritsuka Fujimaru must make the grave decisions and sacrifices that make them either saviors or... destroyers...
Author Notes (A/N)
・I did not own either Kamen Rider Gaim and Fate/Grand Order: Cosmos in the Lostbelt because they've officially belonged to the Toei Corporation and Type-Moon respectively.
・I'm only own both OCs and the synopsis of this story.