Manga Fate/grand Order -Mortalis:stella-

It is the year 2016 and anomalies occurring in the past could be the undoing of humanity's future. The Chaldea Security Organization, formed to safeguard the timeline of mankind as securely as possible, has developed a time-travel technique to rectify these events and ensure humanity's continued existence. However, when an unknown peril endangers the lives of all, rookies Mash Kyrielight and Ritsuka Fujimaru have been chosen to be the saviors and are tasked to locate the Holy Grail and fight against destiny itself.