Fate/Grand Order: Observer on Timeless Temple (2015)

The first season of Fate/Grand Order. Fujimaru Ritsuka, the protagonist, becomes the only available Master that could save humanity from an extinction level event in the near future. They get sent to the past to fix the anomalies and piece together the clues to the reason why humanity is being targeted. Devised by Kinoko Nasu, the original writer of Fate/stay night, and co-written with Higashide Yuichirō and Sakurai Hikaru. There are nine episodes.