Fuyuki Singularity

Fuyuki: The Contaminated City in Flames (炎上汚染都市) is the initial Singularity detected by Chaldea, codenamed Singularity F (特異点F) and located in A.D. 2004.

Setting
The Singularity was located in Fuyuki City, Japan in 2004 AD. At this point in history, a Holy Grail War was taking place in the city. Following the Singularity's manifestation, the city was engulfed in flames and all humans vanished, leaving only the Servants. The Holy Grail War was also disrupted, being switched to something else. Subsequently, a corrupted Saber defeated five of the other Servants, with only Caster surviving. The fallen Servants were also corrupted and rose as Shadow Servants. At the same time, monsters appeared in the city.

The core of the Singularity is Fuyuki's Greater Grail, guarded by Saber.

History
Ritsuka Fujimaru and Mash Kyrielight are suddenly rayshifted to the Singularity following the explosion that destroyed the Chaldea command room. After Mash destroys the skeletons surrounding them, the pair are contacted by Romani Archaman. He confirms that Mash is now fused with a Servant, which allowed her to survive the explosion. Mash suspects the Servant was one provided in advance to investigate the Singularity, but their Master was killed in the explosion. He contracted with her to grant his abilities to her in exchange for eliminating Singularity before vanishing without revealing his True Name. Romani confirms Ritsuka is now Mash's Master. As comms begin to break up, he orders the pair to go to a leyline about 2km from their location to stablize the connection. After comms are cut, Fou is revealed to have rayshifted with Ritsuka and Mash. They then head for the coordinates Romani provided.

The pair eventually find Olga Marie Animusphere being attacked by monsters. After saving her, Mash explains the situation to her. Olga reveals they are the only ones who rayshifted to the Singularity because they weren't in Coffins at the time of the Rayshift. Rayshifting flesh and blood is unlikely to succeed, though not impossible. Meanwhile, Coffins have breakers that cut off the power when the success rate is below 95%. As they're at the leyline point Romani told them of, Mash places her shield on the ground so Olga can establish a summoning circle. With that comms with Romani are reestablished, but Olga demands to speak with Lev Lainur. Romani reveals the surviving staff is less than twenty, including him. He is only in charge of operation because there is no one ranked higher than him who survived. He suspects Lev died in the explosion since he was supervising from the command room. He also reveals the 47 Master candiates are all in critical condition. Olga orders him to put them in cryostasis immediately. She says Ritsuka, Mash, and her will find the cause of the Singularity while Romani repairs Rayshift functionality. Once it's found and Chaldea is restored, she will send in another team. After comms are ended, the group continue to search for the Singularity's source.

Later, Ritsuka recalls how Olga explained how humanity will cease to exist in 2016. Using Laplace and Trismegitus to review data for the last 2000 years, Chaldea eventually observed Singularity F in Fuyuki City in 2004. It is an "unobservable zone" that didn't exist in history up to the year 2015. As the Singularity is suspected of being the cause of what will happen in 2016, the U.N. approved of the operation to rayshift there and destroy it. The original plan was to have Team A of the Master candidates rayshift ahead and establish a base camp, while Team B and below would stay on standby.

Participants
The participants have varied between different mediums.